Telegraph

- Allow to set `domain` (e.g. to use a mirror like graph.org)

- Added async client `telegraph.aio.Telegraph`
- Added `Telegraph.upload_file` (`telegraph.upload_file` is deprecated now)

- Fix `pre` tag: preserve whitespace

- Python 2 is not supported anymore
- Added `telegraph.exceptions.RetryAfterError`

- 25/21 Disable escaping non-ascii characters in json dump (thx weakish)

- 18 Add replacing access token after revoke (thx paradox70)
- 20 Fix throwing `InvalidHTML` exception when there's no start tag (thx blue-bird1)