Breaking changes for a better Gifted Messenger

Breaking: appendMessage, prependMessage are now deprecated, messages list are now managed only using states - See example
Breaking: All messages should now contain a uniqueId property
Breaking: setMessageStatus is now deprecated, use the message attribute status instead
Breaking: New prop isLoadingEarlierMessages to display a loader when loading earlier messages
New prop typingMessage for displaying 'User is typing a message...'
New prop leftControlBar - PR @gnl
Android improvements
react-native-parsed-text has been re-implemented
ESLint implementation - PR @SEthX
ES6 & Example refactoring
Fixing scroll when loading earlier messages
Various fixes and improvements by @swapkats, @ianlin, @zxcpoiu, @cnjon
Special thanks to @yogiben, @koppelaar & @SEthX for their contributions