Upgrade to Android Studio Beta

 - Upgrade Gradle to 2.1
 - Upgrade Android Gradle Build to 0.13.1
 - Upgrade Android Build tools to 20.0.0
 - Upgrade Target SDK Version to 20
 - Fix build.gradle to work with the new versions
Merge pull request #45 from strongloop/feature/upgrade-to-android-studio-beta

Upgrade to Android Studio Beta