Coverted the project to use gradle 1.9 and Android Studio 0.4.2+

Updates
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* Updated the targetSdk & compileSdk to 19
* Project builds with gradle v1.9 via the command line or Android Studio 0.4.2
* Dependencies are now resolved from maven central repo instead of local directories
* In the root HoloGraphLibrary, gradle can now be ran to build the library and sample project in one command.