title: PhoneAuthProvider not working
body: <p>Hello I am working with Firebase Authentication method of Phone Authentication but when I put  that method that time PhoneAuthProvider given me error that not cannot resolve symbol:</p>
  
  <pre><code>  private void resendVerificationCode(String phoneNumber,
                                      PhoneAuthProvider.ForceResendingToken token) {
      PhoneAuthProvider.getInstance().verifyPhoneNumber(
              phoneNumber,        // Phone number to verify
              60,                 // Timeout duration
              TimeUnit.SECONDS,   // Unit of timeout
              this,               // Activity (for callback binding)
              mCallbacks,         // OnVerificationStateChangedCallbacks
              token);             // ForceResendingToken from callbacks
  }
  </code></pre>
  
  <p>I am also </p>
  
  <pre><code> PhoneAuthProvider.ForceResendingToken mResendToken;
   PhoneAuthProvider.OnVerificationStateChangedCallbacks mCallbacks;
  </code></pre>
  
  <p>My Firebase version and also add service file:~</p>
  
  <pre><code> compile 'com.google.firebase:firebase-auth:10.0.1'
   classpath 'com.google.gms:google-services:3.0.0'
  </code></pre>
  
  <p>So how can solve this problem</p>