Refresh gradle configurations

[ZacSweers]

A few things, all to refresh the current gradle configuration to support the latest versions of Android Studio

• Tweaked .gitignore to better handle IntelliJ/Android Studio files
• Update gradle plugin version to latest 1.0.0-rc4
• Add gradle wrapper for easy project import
• Updates plugin names to new versions (previous versions were deprecated and will break soon)
• Update build and compile SDK versions to latest
• Remove unnecessary gradle plugin version and repositories declarations, as these are set via the top-level build.gradle file
• Update target SDK version to latest 21
• Specify min and target SDK versions that match the manifests
• Update README.md to use syntax highlighting in its code samples
• Updated version checking for Lollipop (see e3db139)

Tested the sample and everything still works as normal, and everything should still continue to work fine in Eclipse as well :)

[ZacSweers]

If there's anything you don't want in this PR (such as the tweaks to the README and version checking), let me know and I'll remove those commits