More documentation work, changed addUsersToGroup back to taking a list of user IDs

Created new README, and finished `intro`

docs/api.rst

@@ -13,10 +13,13 @@ If you are looking for information on a specific function, class, or method, thi
 Client
 ------
 
-.. todo::
-    Write introduction text about `Client`, and add documentation for all events
+This is the main class of `fbchat`, which contains all the methods you use to interract with Facebook.
+You can extend this class, and overwrite the events, to provide custom event handling (mainly used while listening)
 
-.. autoclass:: Client(email, password, user_agent=None, max_retries=5, session_cookies=None, logging_level=logging.INFO, set_default_events=True)
+.. todo::
+    Add documentation for all events
+
+.. autoclass:: Client(email, password, user_agent=None, max_retries=5, session_cookies=None, logging_level=logging.INFO)
     :members:
 
     .. automethod:: sendRemoteImage(image_url, message=None, thread_id=None, thread_type=ThreadType.USER)
@@ -33,6 +36,7 @@ A good tip is to write ``from fbchat.models import *`` at the start of your sour
 
 .. automodule:: fbchat.models
     :members:
+    :undoc-members:
 
 
 .. _api_utils: