Create a Fragment layout for the timeline
Switch activity timeline to use fragment layout
Implement Home Timeline as a fragment

- Create base TweetsListFragment
- Create a HomeTimelineFragment that extends the above
- Move relevant logic to base fragment and out of the activity
Support fetching mentions
Implement initial Mentions Fragment
Add a FragmentTabListener to add support for tabs
Add tabs for Home and Mentions tweets.

- Users can switch between timeline and mentions views using tabs
Merge branch 'fragments' into dev