Added functionality to share and edit code

Hello, a couple of friends and i were taking part in the mcgill hackathon that happened last weekend and we used ur project to add a feature the can allow sharing and editing code. we saw from ur project that that was ur next step after the chat system. doing this project gave us an ability to learn how to contribute to open source as half the hackathon was spent figuring out the code and learning coffeescript/jade/nodejs/express for the very first time. For the hackathon, we did redesign the front end since we had a front end developer in the team and demoed with our design but in this pull request, ur front-end is still the same. we got the code sharing bit to work in a way that was real time too (i.e. if the code window is open in both sides of the chat, then clicking Propogate Hack would instantaneously modify code in both windows). We also added a Code button to open the modal (but u can still use <hack>). We also used MongoHQ instead of MongoLab. Hope this feature is a good addition/hack to your project :)