Use AppCompat To Support Material Design on Pre-Lollipop releases. Fixes T1018

Summary:
  - Theme App with AppCompat Library's theme.
  - Switch to using new Toolbar widget to implement ActionBar.

Known issue. CAB appear on top of the Actionbar instead of
replacing it. Seems like a framework bug. I have a workaround in
mind but it's ugly. I'll investigate better way of fixing it.

Test Plan:
  - Install attached apk.
  - Launch app.
  - See Material Design's ActionBar in action

Reviewers: dkobia, PapaLee

Subscribers: rjmackay, shadowhand

Maniphest Tasks: T1018

Differential Revision: https://phabricator.ushahidi.com/D470