Replacing Socket.IO with Primus

... and SockJS.

Still need to re-implement a few things, test and solve those
disconnection issues.
Merge remote-tracking branch 'origin/master' into primus-integration
Prevent crash when CJ is missing from waiting list

TODO: find root cause!
Refactoring back-end: new Tournament module
Back-end refactoring cont.
Back-end refactoring cont.

User module + identification process
Identification and identity confirmation processes
Open/close ring
CJ authorisation process

TODO: rejected and ringIsFull events
ringNotJoined/cjRejected events
Improved JP's CJ events (authorise, reject, remove)
Tidying previous commit
User exit functions
Session restoration + notify JP when CJ exits
Scoring state
Scoring
Merge pull request #7 from axelboc/primus-integration

Primus integration and full back-end refactoring