Several documentation enhancements and build warnings fixes

- Made the documentation even more friendly towards newbies.
- Eased the usage of methods like get history which now set
  a default empty message for message actions and vice versa.
- Fixed some docstring documentations too.
- Updated the old normal docs/ to link back and forth RTD.
- Fixed the version of the documentation, now auto-loaded.

telethon/tl/custom/dialog.py

@@ -24,10 +24,7 @@ class Dialog:
         self.unread_count = dialog.unread_count
         self.unread_mentions_count = dialog.unread_mentions_count
 
-        if dialog.draft:
-            self.draft = Draft(client, dialog.peer, dialog.draft)
-        else:
-            self.draft = None
+        self.draft = Draft(client, dialog.peer, dialog.draft)
 
     def send_message(self, *args, **kwargs):
         """