FIRMessagingModule is not abstract and does not override abstract method onActivityResult

Using:
```
react-native: 0.39.0
react-native-fcm: 2.5.2
```

Building for Android (have not tested iOS):

```
/.../node_modules/react-native-fcm/android/src/main/java/com/evollu/react/fcm/FIRMessagingModule.java:36: error: FIRMessagingModule is not abstract and does not override abstract method onActivityResult(int,int,Intent) in ActivityEventListener
public class FIRMessagingModule extends ReactContextBaseJavaModule implements LifecycleEventListener, ActivityEventListener {
^
/.../node_modules/react-native-fcm/android/src/main/java/com/evollu/react/fcm/FIRMessagingModule.java:274: error: method does not override or implement a method from a supertype
@Override
^
/.../node_modules/react-native-fcm/android/src/main/java/com/evollu/react/fcm/FIRMessagingModule.java:278: error: method does not override or implement a method from a supertype
@Override
^
3 errors
:react-native-fcm:compileReleaseJavaWithJavac FAILED

FAILURE: Build failed with an exception.
```

I've seen some other similar issues here (all closed) that seem to indicate different solutions, but they did not work in my case.

Note: in code above I replaced my local path with `...` for privacy and brevity.

Start with android/src/main/java/com/evollu/react/fcm/FIRMessagingModule.java, especially the class declaration near line 36 and the methods near lines 274 and 278. Compare the ActivityEventListener API used by react-native 0.39.0 with this module, then run the Android release build; done means the module compiles without these Java errors.

Written by the indexing model from the issue text.