separates versioning for firebase-core and firebase-messaging.  These are no longer coupled in recent releases by Google.

fixed sub_text displaying for android when picture has specified. tested on android 5 API 21 emulator

This reverts commit 496e2893.

This is needed when the strings are encoded in utf8. The encoding is needed for special characters (as simple as é) and smileys. 
In my use case, I only need title, body and big_text (not familiar with the new additions: action, etc.) but any string in the notification could need decoding. 
String X = bundle.getString("X")
X= URLDecoder.decode( X, "UTF-8" );

Medium term, it could be nice to have a tag for encoding in the initial message that would trigger or not a decoding.