Upgrade connect to v2

This commit upgrades connect dependency to v2.x and should fix https://github.com/josephg/ShareJS/issues/120

I didn't remove the connect dependencies totally because node-browserchannel is modeled as a connect middleware hence it's going to take a lot of effort to remove connect.

With this change, `rest.coffee` is modeled as a rest middleware as well ( and may be taken out from sharejs core like node-browserchannel ? )