fix crash when user use Undo after sending text message
Merge pull request #511 from alr/develop

fix crash when user shakes-to-undo after sending text message. close #508
Merge branch 'develop' into release-6.0
fix #514
update cocoapods
rebuild xcode project - fuck you xcode. update assets (#). clean up file imports. use modern objC. update podfile.
update assets #502. begin JSQMessagesMediaPlaceholderView. #504
turn off springiness in demo
implement basic placeholder media view. #504
adjust typing indicator view
fix JSQMessagesTypingIndicatorFooterView layout constraints
formatting. update comments
remove duplicate constraints in cell xibs.
resolve TODOs
finished docs for JSQMessagesMediaPlaceholderView
update JSQMessageMediaData docs
update demo for async loading example
Merge branch 'release-6.0' of https://github.com/jessesquires/JSQMessagesViewController

Conflicts:
	JSQMessages.xcodeproj/project.pbxproj
	JSQMessagesViewController/Views/JSQMessagesCollectionViewCellIncoming.xib
	JSQMessagesViewController/Views/JSQMessagesCollectionViewCellOutgoing.xib