feat(*): connecting the caller and callee

The flow:
1. Ready. Both clients, the caller and callee are telling each other when the room view is loaded.
2. Sharing. Both clients, the caller and callee are telling each other the username and room ID.
3. Connecting. After everything is ready and room ID is known, then start the peer connection.

Important notes:
- Since we are using the customized version of PeerConnection.js without having a unit test, the current implementation is buggy. When we are using this plugin and run it on the application, we will have this PeerConnection.js add video element a couple of times on the room view.