Added
* Add method for uploading files to chat.
* Add method for downloading files from chat.
Changed
* Add `data` and `files` fields to `HTTPRequest` for sending multipart/form-data in request.
* Add `expected_type` field to `HTTPRequest` and `expected_type` property to `BaseBotXMethod`
to allow interacting with non JSON responses.
* Add `should_process_as_error` field to `HTTPRequest` so that errors that are not in
the range of 400 to 599 can be added.
* Add `raw_data` to `HTTPResponse`so that you can process raw content of response.