Improve code exapmle in "Doing stuff" section

I noticed that there is no initialization of `me` variable. But finally I decided to copy the whole example from docs because it contains more useful code and comments.

README.rst

@@ -46,12 +46,29 @@ Doing stuff
 
 .. code:: python
 
-  print(me.stringify())
+  # Getting information about yourself
+  print(client.get_me().stringify())
 
-  client.send_message('username', 'Hello! Talking to you from Telethon')
+  # Sending a message (you can use 'me' or 'self' to message yourself)
+  client.send_message('username', 'Hello World from Telethon!')
+
+  # Sending a file
   client.send_file('username', '/home/myself/Pictures/holidays.jpg')
 
-  client.download_profile_photo(me)
+  # Retrieving messages from a chat
+  from telethon import utils
+  for message in client.get_message_history('username', limit=10):
+      print(utils.get_display_name(message.sender), message.message)
+
+  # Listing all the dialogs (conversations you have open)
+  for dialog in client.get_dialogs(limit=10):
+      print(utils.get_display_name(dialog.entity), dialog.draft.message)
+
+  # Downloading profile photos (default path is the working directory)
+  client.download_profile_photo('username')
+
+  # Once you have a message with .media (if message.media)
+  # you can download it using client.download_media():
   messages = client.get_message_history('username')
   client.download_media(messages[0])