Integration of Gradle and removed a png that caused a compilation error

* Integration with the new Gradle-based android build system as well as the Android Studio IDE
* CropperSample/res/drawable-xhdpi/cheetahs.png is not considered as a png file by aapt
Add intellij files/folder to .gitignore
Merge pull request #16 from kokaz/master

Integration of Gradle and removed a png that caused a compilation error