The idea was nice, but it really complicated things for us and for the
user.
If a user wants to run more than one handler on an update, he can put
the handlers in different groups or he can have a single handler.
If a user wants to have multiple handlers in the same group which only
one of them should run on the update, he should use check_update().
Since we haven't released this code yet, there's no problem with
backward compatability.
* 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
