Move application lifecycle tracking in Android to the native wrapper

[kadikraman]

Fixes #36

Bug

Application lifecycle events (Application Installed, Opened, Updated) in Android are not being tracked.

Cause

In the analytics-android package, lifecycle events being tracked in the callback of onActivityCreated. However, neither onActivityCreated or onActivityStarted are ever called when using this library via the native wrapper. The other lifecycle methods, e.g. onActivityResumed, onActivityPaused, onActivityStopped etc are called as expected, which makes this a React Native specific bug.

The most likely reason for this is that MainActivity is created to run the React Native app before the native Analytics client is initialised, so that onActivityCreated and onActivityStarted for the MainActivity would have been triggered before the Analytics client has subscribed to them.

Solution

Move the lifecycle tracking code into the native wrapper.

The logic for lifecycle tracking is mirrored exactly as in analytics-android, and the trackAppLifecycleEvents flag will no longer be passed down to the native package, but handled in the wrapper.

Testing

Tested locally using Android Studio and a Nexus emulator, running Android 8.
Confirmed that each of the three lifecycle events are correctly sent and can be seen in the Live Debugger (https://app.segment.com/[name]/sources/android/debugger)

[f2prateek]

Merged #74. Let's rebase this, and the build should pick up the fixed config.