Django-telegram-login

Done:
- [x] Added coverage.
- [x] Extended documentation.
- [x] Refactored logic and tests.

Implemented:
- [x] The corner radius supporting.

Implemented:
- [x] Documentation;
- [x] Customizing 6 types of widgets;
- [x] Redirect and callback handling of user data;
- [x] Convenience Telegram script insertion to html.