HTML5: cleanup and fix errors when a new user joins the session

Most changes on the method WebsocketConnection#_onUserConnected()
The server doesn't crash as much as before when a user joins.
HTML5: restructuring the classes in the node.js server

Restructured the classes that read or write on redis to make more sense. Now
there's a single class that makes the bridge between redis and websockets,
and helper classes to publish to redis and to do any other actions on redis.
HTML5: update redis to 0.9.0, solves a few bugs

Apparently solved errors on user joins, the error was:
Error: node_redis command queue state error. If you can reproduce this, please report it
HTML5: fixing undo and clearPaper events in the server
HTML5: comment out wrong method call in RedisPublisher

Temporary, the method called doesn't exist anymore. Have to check it better,
but commented it for now so the app doesn't break.
Merge pull request #288 from daronco/html5-bridge-server-refactor-2

HTML5 server refactoring 2