title: Error:(31, 32) error: cannot find symbol class AuthCredential
body: <p>Cannot import the following when working with firebase</p>
  
  <pre><code>    import com.google.firebase.auth.AuthCredential;
      import com.google.firebase.auth.AuthResult;
      import com.google.firebase.auth.FirebaseUser;
  </code></pre>
  
  <p>Gradle File</p>
  
  <pre><code>compile 'com.google.android.gms:play-services-auth:9.6.1'
  compile 'com.google.firebase:firebase-database:9.2.1'
  compile 'com.firebase:firebase-client-android:2.5.0'
  compile 'com.google.firebase:firebase-core:9.2.0'
  compile 'com.google.firebase:firebase-auth:9.2.1'
  compile 'com.google.firebase:firebase-auth:9.4.0'
  compile 'com.google.firebase:firebase-config:9.4.0'
  compile 'com.google.android.gms:play-services-ads:9.6.1'
  compile 'com.google.firebase:firebase-crash:9.4.0'
  
  compile 'com.android.support:design:24.2.1'
  compile 'com.android.support:support-v4:24.2.1'
  </code></pre>
  
  <p>Is i need anything extra to add to compile</p>