Upgrade to the latest version of gradle plugin

This is to resolve 'The project is using an unsupported
version of the Android Gradle plug-in' error.
Also, updated SDK build tools version to 19.1.
Removed unnecessary public method onFaqClicked()
Smoother scrolling in about screen
Merge pull request #399 from ozbek/master

Upgrade to the latest version of gradle plugin and some minor fixes in About screen