Note that Proguard 4.4 (which is currently included in the Android SDK) is to buggy and creates an apk that crashes at startup. Proguard 4.6 works. See https://code.google.com/p/android/issues/detail?id=18371
Removed Markdown jar as it is not used.
Included "library dependency" jars that aren't used at runtime by the application but are referred to by the libraries the application uses and therefore are required by Proguard.
Bump Android target to 9, as there are some reflection references to classes in Android version 9.