added getRooms

[Dshankar]

Example use cases:

1. A chat app that lists all the "chat lobbies" that a user may join
2. User wants to create a new "chat lobby" but it needs to be unique. This allows the app to lookup existing lobbies to verify uniqueness.

[cayasso]

I will merge this in but will do some changes to leverage existing api.

[cayasso]

@Dshankar check this commit c4d4d6f it basically add rooms method which already exist on the spark to the server (primus)

primus.rooms(); // get all active rooms

or

primus.rooms(spark) // get the rooms spark is in

Thanks again for your initiative

Will be releasing new version soon.

[Dshankar]

I wrote some tests as well but didn't merge. I see that you have done so already! Nice work, and thanks for a great lib!