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

Created new README, and finished `intro`

examples/fetch.py

@@ -0,0 +1,50 @@
+# -*- coding: UTF-8 -*-
+
+from fbchat import Client
+from fbchat.models import *
+
+client = Client("<email>", "<password>")
+
+# Fetches a list of all users you're currently chatting with, as `User` objects
+users = client.getAllUsers()
+
+print('user IDs: {}'.format(user.uid for user in users))
+print("user's names: {}".format(user.name for user in users))
+
+
+# If we have a user id, we can use `getUserInfo` to fetch a `User` object
+user = client.getUserInfo('<user id>')
+# We can also query both mutiple users together, which returns list of `User` objects
+users = client.getUserInfo('<1st user id>', '<2nd user id>', '<3rd user id>')
+
+print('User INFO: {}'.format(user))
+print("User's INFO: {}".format(users))
+
+
+# `getUsers` searches for the user and gives us a list of the results,
+# and then we just take the first one, aka. the most likely one:
+user = client.getUsers('<name of user>')[0]
+
+print('user ID: {}'.format(user.uid))
+print("user's name: {}".format(user.name))
+
+
+# Fetches a list of all threads you're currently chatting with
+threads = client.getThreadList()
+# Fetches the next 10 threads
+threads += client.getThreadList(start=20, length=10)
+
+print("Thread's INFO: {}".format(threads))
+
+
+# Gets the last 10 messages sent to the thread
+messages = client.getThreadInfo(last_n=10, thread_id='<thread id>', thread_type=ThreadType)
+# Since the message come in reversed order, reverse them
+messages.reverse()
+
+# Prints the content of all the messages
+for message in messages:
+    print(message.body)
+
+
+# Here should be an example of `getUnread`