Upgrade Android Gradle plugin to v0.14.2. Fixes T1115

Summary:
 - Upgrade Android Gradle plugin to v0.14.2
 - Change deprecated runProguard to minifyEnabled

Test Plan:
Run

 - `./gradlew build`

Reviewers: dalezak, dkobia

Subscribers: rjmackay

Maniphest Tasks: T1115

Differential Revision: https://phabricator.ushahidi.com/D506