Android Studio 1.0

Updating Android Studio to 1.0 stable and removing postflight task.

As I said on this Pull Request https://github.com/caskroom/homebrew-versions/pull/595 , Android Studio can be set to use JDK other than 6.
The postflight task was causing trouble for Android Studio to auto update.
So, it's better to users to change if needed and still have auto update working.

Using caveats to inform user about how to change the JDK