Sort room names

With a sizeable list of rooms managed by the bot, it can get
a little hard to find a specific room in the list if they
are added in random order. To make it a little easier to
visually parse the list, sort the room names.

Change-Id: Ia68c36346ea5fe542b6708a3f02ea911f348bc36

ptgbot/db.py

@@ -49,7 +49,7 @@ class PTGDataBase():
         return room in self.data['rooms']
 
     def list_rooms(self):
-        return self.data['rooms']
+        return sorted(self.data['rooms'])
 
     def add_rooms(self, rooms):
         for room in rooms: