Update SDK/Tools to latest, use Maven instead of git submodule for FB SDK

- Removed the facebook-sdk submodule.  Let's use Maven (dependencies automatically resolved by Android Studio) because it's a lot cleaner.
- Updated Android build tools and support library to latest.
- Raise minSdkVersion to 9 to match latest Parse SDK.
- Updated the README to only focus on setup instructions for Android Studio, which is becoming the more preferred IDE instead of Eclipse.
This should use `provided` since `facebook-android-sdk` isn't required by ParseUI, right? If so, we'll also need to add `facebook-android-sdk` to the necessary sample projects gradle files.