removed unused imports in FirestackAuth.java

Author: Salakar

android/src/main/java/io/fullstack/firestack/FirestackAuth.java

@@ -8,7 +8,6 @@
 
 import android.net.Uri;
 import android.support.annotation.NonNull;
-import android.support.annotation.Nullable;
 
 import com.facebook.react.bridge.Arguments;
 import com.facebook.react.bridge.ReactApplicationContext;
@@ -17,15 +16,12 @@
 import com.facebook.react.bridge.Callback;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.bridge.ReadableMap;
-import com.facebook.react.bridge.ReadableNativeMap;
-import com.facebook.react.modules.core.DeviceEventManagerModule;
 import com.facebook.react.bridge.ReactContext;
 
 import com.google.android.gms.tasks.OnCompleteListener;
 import com.google.android.gms.tasks.OnFailureListener;
 import com.google.android.gms.tasks.Task;
 import com.google.firebase.FirebaseApp;
-import com.google.firebase.FirebaseOptions;
 
 import com.google.firebase.auth.AuthCredential;
 import com.google.firebase.auth.AuthResult;