Retrofit2

Boa Tarde,
Pessoal alguém poderia me ajudar na Implementação do Retrofit2, está retornando erro e já li a documentação, porém estou com dificuldades.

Information:Gradle tasks [:app:assembleDebug]
Error:Error converting bytecode to dex:
Cause: java.lang.RuntimeException: Exception parsing classes
Error:1 error; aborting
Error:Execution failed for task ':app:transformClassesWithDexForDebug'.
> com.android.build.api.transform.TransformException: java.lang.RuntimeException: java.lang.RuntimeException: com.android.ide.common.process.ProcessException: java.util.concurrent.ExecutionException: com.android.ide.common.process.ProcessException: Return code 1 for dex process
Information:BUILD FAILED
Information:Total time: 19.279 secs
Information:3 errors
Information:0 warnings
Information:See complete output in console

02-01 10:55:19.402 1828-1836/? W/MessageQueue: Handler (android.os.Handler) {2df742d} sending message to a Handler on a dead thread
                                               java.lang.IllegalStateException: Handler (android.os.Handler) {2df742d} sending message to a Handler on a dead thread
                                                   at android.os.MessageQueue.enqueueMessage(MessageQueue.java:543)
                                                   at android.os.Handler.enqueueMessage(Handler.java:643)
                                                   at android.os.Handler.sendMessageAtTime(Handler.java:612)
                                                   at android.os.Handler.sendMessageDelayed(Handler.java:582)
                                                   at android.os.Handler.post(Handler.java:338)
                                                   at android.os.ResultReceiver$MyResultReceiver.send(ResultReceiver.java:57)
                                                   at com.android.internal.os.IResultReceiver$Stub.onTransact(IResultReceiver.java:58)
                                                   at android.os.Binder.execTransact(Binder.java:565)

Abaixo minha Implementação.
Metodo Main

package victoroliveira.com.br.loja;

import android.content.Intent;
import android.os.Bundle;
import android.support.design.widget.FloatingActionButton;
import android.support.design.widget.NavigationView;
import android.support.v4.view.GravityCompat;
import android.support.v4.widget.DrawerLayout;
import android.support.v7.app.ActionBarDrawerToggle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.Toolbar;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;

import java.util.List;

import retrofit2.Call;
import retrofit2.Callback;
import retrofit2.Response;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import victoroliveira.com.br.loja.Models.cliente;

public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener {
    private static final String TAG = "ERRO" ;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl(clienteService.BASE_URL)
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        clienteService service = retrofit.create(clienteService.class);
        Call<List<cliente>> call = service.getcliente();
        call.enqueue(new Callback<List<cliente>>() {
            @Override
            public void onResponse(Call<List<cliente>> call, Response<List<cliente>> response) {

                if (!response.isSuccessful()){
                    Log.i("TAG","ERRO: " + response.code());
                }else{

                }
            }

            @Override
            public void onFailure(Call<List<cliente>> call, Throwable t) {

                Log.e(TAG,"ERRO: " + t.getMessage());
            }

        });

        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);
        setSupportActionBar(toolbar);

        final FloatingActionButton fab = (FloatingActionButton)findViewById(R.id.fab);

        fab.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                Intent fab = new Intent(MainActivity.this,TelaAdd.class);
                startActivity(fab);
            }
        });

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(
                this, drawer, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close);
        drawer.setDrawerListener(toggle);
        toggle.syncState();

        NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);
        navigationView.setNavigationItemSelectedListener(this);
    }

    @Override
    public void onBackPressed() {
        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        if (drawer.isDrawerOpen(GravityCompat.START)) {
            drawer.closeDrawer(GravityCompat.START);
        } else {
            super.onBackPressed();
        }
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }

    @SuppressWarnings("StatementWithEmptyBody")
    @Override
    public boolean onNavigationItemSelected(MenuItem item) {
        // Handle navigation view item clicks here.
        int id = item.getItemId();

        if (id == R.id.nav_camera) {
            // Handle the camera action
        } else if (id == R.id.nav_gallery) {

        } else if (id == R.id.nav_slideshow) {

        } else if (id == R.id.nav_manage) {

        } else if (id == R.id.nav_share) {

        } else if (id == R.id.nav_send) {

        }

        DrawerLayout drawer = (DrawerLayout) findViewById(R.id.drawer_layout);
        drawer.closeDrawer(GravityCompat.START);
        return true;
    }
}

METODO INTERFACE

package victoroliveira.com.br.loja;

import java.util.List;

import retrofit2.Call;
import retrofit2.http.GET;
import victoroliveira.com.br.loja.Models.cliente;

/**
 * Created by Victor Oliveira on 30/01/2017.
 */

public interface clienteService {

    public  static final String BASE_URL = "http://192.168.0.143:21590/Mobile/services/";

    @GET("{cliente}")
    Call<List<cliente>> getcliente();

}


CLASSE cliente

package victoroliveira.com.br.loja.Models;

/**
 * Created by Victor Oliveira on 30/01/2017.
 */
public class cliente {
    private Long id;
    private String nome;
    private Long cpf;
    private String produto;
    private String logradouro;
    private String n;
    private String cidade;
    private String pais;
    private Long telefone;
    private String razaosocial;
    private String nomefantasia;
    private String username;
    private String senha;


    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getNome() {
        return nome;
    }

    public void setNome(String nome) {
        this.nome = nome;
    }

    public Long getCpf() {
        return cpf;
    }

    public void setCpf(Long cpf) {
        this.cpf = cpf;
    }

    public String getProduto() {
        return produto;
    }

    public void setProduto(String produto) {
        this.produto = produto;
    }

    public String getLogradouro() {
        return logradouro;
    }

    public void setLogradouro(String logradouro) {
        this.logradouro = logradouro;
    }

    public String getN() {
        return n;
    }

    public void setN(String n) {
        this.n = n;
    }

    public String getCidade() {
        return cidade;
    }

    public void setCidade(String cidade) {
        this.cidade = cidade;
    }

    public String getPais() {
        return pais;
    }

    public void setPais(String pais) {
        this.pais = pais;
    }

    public Long getTelefone() {
        return telefone;
    }

    public void setTelefone(Long telefone) {
        this.telefone = telefone;
    }

    public String getRazaosocial() {
        return razaosocial;
    }

    public void setRazaosocial(String razaosocial) {
        this.razaosocial = razaosocial;
    }

    public String getNomefantasia() {
        return nomefantasia;
    }

    public void setNomefantasia(String nomefantasia) {
        this.nomefantasia = nomefantasia;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getSenha() {
        return senha;
    }

    public void setSenha(String senha) {
        this.senha = senha;
    }
}