fix travis
improve KVO. better handle add/remove observers. close #285
fix bubble glitchy “bounce” on view appear and swipe back/forward in nav controller.
fix #368
fix issue where load earlier messages header or typing indicator would not appear.
don’t auto scroll when showing typing indicator. update docs for typing indicator footer and load messages header.
improve swipe back keyboard animation using view snapshot.
fix header/footer background colors
Merge commit 'a98115d4cd1fea5f65be875968bda5758735f6c8' into media

Conflicts:
	JSQMessagesDemo/JSQDemoViewController.m
	JSQMessagesViewController/Controllers/JSQMessagesViewController.m