Support Android activity aliases

Fix type Listner to Listener

Just return the className. The old code didn't work with activity aliases. For example, when launching with `<activity-alias android:name=".SplashActivity" android:targetActivity=".MainActivity" />`, the old code would try to get the class for `SplashActivity` which threw `ClassNotFoundException`.

Thank you for the nice library.
Fixed typo to sample source code.

Update README.md

Fix call to setApplicationIconBadgeNumber

added big picture style to android notification

Recommend staying on iOS SDK v3

Provide collapse_key, from, mesage_id, and send_time in foreground notificaitons

doc(readme) : add missing settings

Update README.md