Server: fix the websocket api
SidebarApp: send a talkilla.sidebar-ready event to the worker
Refactor a lot of duplicated code in the worker tests
Worker: implement a tryPresenceSocket method

This method try to attach a websocket with the provided information, if it
fails, then it means the login expired.
Worker: try to attach a websocket when receiving the talkilla.sidebar-ready event
Worker: fix the tests
Worker: implement a _setUserProfile method
Worker: re-attach the websocket
SidebarApp: use a cookie for persistant login
Server: do not logout people that comes offline
SidebarApp: do not logout when leaving the page
Fix tests
Set an expiration time for the cookie
added ringtone file
basic implementation of ringtone
refactored Call model to accept an options object
Server: allow users to be logged in but not present.
Worker: reuse _setupWebSocket
Fix jshint errors
merge with ignore-a-call branch