Gradle Refresh

 - move common functions to functions.gradle
 - use dependency aliases whenever possible
 - update to gradle 2.1
 - cleanup build.gradle files with proper spacing
 - remove duplicated blocks
 - compile incrementally (java)

Gradle Refresh v2

 - alphabetical order dependencies
 - added jdk8 to build tests
 - moved script to file for travis

Gradle Refresh v2a

 - fix travis
 - remove pointless logging

jdk8 isn't ready for travis
Merge pull request #94 from iBotPeaches/gradle_refresh

Gradle Refresh
Merge branch 'master' of https://github.com/iBotPeaches/Apktool