'Searches for users in directory
Returns:
dict of the form::
"limited": <bool>,  # whether there were more results or not
"results": [  # Ordered by best match first
"user_id": <user_id>,
"display_name": <display_name>,
"avatar_url": <avatar_url>'

def search_users(self, user_id, search_term, limit):

    return self.store.search_user_dir(user_id, search_term, limit)
