Add coffeescript compilation to gruntfile

Plain and simple. You still have to have coffee-script installed globally, but this takes care of watching your files and compiling it automagically. AND - `uglify` gets called automatically since the `coffee` grunt creates a js file, which triggers the `uglify` command to run and minimize that bad boy.

@darrenjaworski please review this, and maybe give it a test whirl if you have time