* initial commit for conversationhandler and example
* implement simple Promise for run_async/conversationhandler
* refactor Promise._done to done
* add handling for timed out Promises
* correctly handle promises with None results
* fix handling tuple states
* update comments on example
* Added a first test on the ConversationHandler.
* Fixed a small typo.
* Yapf'd.
* add sphinx doc for conversation handler
* fix title for callbackqueryhandler sphinx docs
