Parse Android SDK, Facebook and ProGuard

If you're logging into Facebook via the Parse Android SDK and are building your application package (apk) with ProGuard enabled, here's what you'll need to add to your proguard-project.txt file:

# need this for Facebook SDK
-keepattributes Signature

-dontwarn com.facebook.**
-dontwarn com.parse.**

-keep class com.facebook.** { *; }
-keep class com.parse.** { *; }