XHR sending is now handled exclusively by XHR.js
HTMLFile inherits from XHR for POST handling
Implemented heartbeats echoing
Events integrated directly into socket.js
New default method to add events is `on`.
Added aliases for old event handling methods
Simplified utilities / removed legacy code
Updated build.js
Actually implemented the private method _get for XHR transports (we were overriding connect() before)
Updated example/API