Use express.js instead of Sinatra for stubbing the back-end

Express can be easily controlled via grunt as part of a more seamless development workflow.  Running `grunt server` spins up the server and starts a watch on files.  Any files that change trigger tests and automatically reload the browser to show changes (via LiveReload plugin).

It also avoids context switching between languages.  The app is written in CoffeeScript and is fairly minimal.

Just add routes and responses.
Merge pull request #7 from meducation/express

Use express.js instead of Sinatra for stubbing the back-end