BaseServer.handle_error() default behaviour is to print to stdout or
stderr (depends on the python version). In case that the file descriptor
is closed an additional exception will be raised, causing the webhook
thread to quit.
Fixes#970
* bot.py: add create_references method
* create bot reference in webhook handler, use create_references on new updates
* message.py: implement reply_text
* echobot2.py: use Message.reply_text
* fix create_references in webhook handler
* add some more instance methods
* Chat.kick_member and unban_member
* bot.py: Create bot references in outgoing messages
* add tests for everything testable
* test_updater.py: add create_references method to MockBot
* remove Bot.create_references and refactor TelegramObject.de_json to take the additional parameter bot
* List bot as named kwarg where used
* file.py: Use Bot.request property instead of Bot._request attr
