Gradle wrapper - recommended way to run gradle on different platforms.

The wrapper automatically download specified version of gradle (in our
case 2.0) and provides the same functionality as standalone gradle
(e.g., installed via brew).

This is next step towards proper CI in H2O-dev.

For more information see here:
http://www.gradle.org/docs/current/userguide/gradle_wrapper.html
Move files from ci folder under gradle folder to follow recommended
conventions.