Required fixes:
- CallbackQuery is now comparable.
- Message.effective_attachment, Message.photo,
Message.new_chat_members, Message.new_chat_photo &
Game.text_entitties semantic fixes - when they are not defined,
return an empty list.
- Docstring fix to Update class.
* Added methods to generate the original markdown/html formatted string from the entities contained in an update
* Added
* Moved the html/markdown parsing methods to `Message`
* Moved extract_* methods from helpers to the appropriate location
* Refactored text_markdown and text_html
* Refactored text_markdown and text_html for efficiency
* Fixed method call in conversationhandler
* Fixed method call in handler
* Fixed `make test` command on windows systems
* Improved method documentation
