wip: add google analytics

Initial attempt at implementing Google Analytics as mentioned at https://github.com/OneBusAway/onebusaway-android/issues/105. I haven't been able to work on this as much as I'd like to and I'd still like to compare this more with the iOS implementation to make sure they have similar events reported. Despite some work still being required it'd be great if I could get some feedback on the progress so far.

Implements [Google Analytics SDK v4 for Android](https://developers.google.com/analytics/devguides/collection/android/v4/) via the [Google Play Services SDK](https://developer.android.com/google/play-services/index.html). Bumps min SDK from 8 to 9 since GA was added in Google Play services, Version 4.3 which does not support SDK 8.