title: Bind ButterKnife to Dialog fails
body: <p>I try to bind ButterKnife to a AleterDialog that i made with a DialogBuilder method
  And exist this method <code>ButterKnife.bind(Object,Dialog);</code> but dosen't work for me</p>
  
  <pre><code>import android.support.v4.app.DialogFragment;
  import android.support.v7.app.AlertDialog;
  public class NewUserDialogFragment extends DialogFragment {
      @Bind(R.id.textuserAccount)
      EditText textuserAccount;
      @Bind(R.id.textPassword)
      EditText textPassword;
      @Bind(R.id.nauta_domains)
      Spinner nauta_domains;
      @Bind(R.id.manualConfig)
      View manualConfig;
      @Bind(R.id.checkViewPass)
      CheckBox checkViewPass;
  
      @NonNull
      @Override
      public Dialog onCreateDialog(Bundle savedInstanceState) {
  
          AlertDialog dialog = new AlertDialog.Builder(getActivity())
                  .setIcon(R.drawable.new_user_dialog__icon)
                  .setTitle(R.string.new_user_dialog_title)
                  .setView(R.layout.accountlist_dialog_user_)
                  .setPositiveButton(R.string.alert_dialog_create, void_OnClickListener)
                  .setNegativeButton(R.string.alert_dialog_cancel, void_OnClickListener)
                  .create();
        //Fails!!!!!!!
          ButterKnife.bind(this,dialog);  
      ...
  </code></pre>
  
  <p>ERROR:</p>
  
  <pre><code>Caused by: java.lang.IllegalStateException: Required view 'textuserAccount' with ID 2131624044 for field 'textuserAccount' was not found. If this view is optional add '@Nullable' annotation.
                                                                                        at butterknife.ButterKnife$Finder.findRequiredView(ButterKnife.java:140)
  </code></pre>
  
  <p>and <code>textuserAccount = (EditText) ((Dialog) dialog).findViewById(R.id.textuserAccount);</code> works perfectly</p>
  
  <p>I can use butterknife somehow in this class?</p>