* Added IsEcho in Message which is indicator of own messages
* Added QuickReply in Message for sending of quick reply buttons with message
* Added mux parameter in Messenger constructor. It is useful when single go app processes the several bots
* Added Messenger.SenderAction which allows to show writing and reading status
* Added Messenger.GreetingSetting and Messenger.CallToActionsSetting which allow to set the bot settings
* Fixed bug with nil returning instead of error object
* Added Read message support
Delivered message suppport already existed but was commented as
indicating that a message was read by a user. As of the 1 July
2016 API release this isn't true, there is another event. This
commit adds read event support and corrects the description of
delivered events. Also added to the example bot.
* go fmt
* Added new profile fields from July 1st API update
* gofmt
