Ignore .DS_Store files.
Implement small functionality inside Qiscus library.

Here's the list of the implemented functionalities:
1. Room loading callback on User.
2. Finding Room of a certain Topic.
3. Topic deletion on Room.
Implement Qiscus listeners for Room and Topic events.
OCD.
Add a little documentation on Angular-based Qiscus API client.
Insert Room's channel code when loading Rooms.
Load and configure Qiscus listener.