moar documentation nitpicks

[Sophrinix]

It should be noted in the documentation that when you run rake, if it immediately fails to compile the coffee-script, you may need to install coffee-script. I was shocked that I needed to do this as I have rails 3.2.x installed and nodejs through npm.

Anyway you may need to run npm install -g coffee-script.

this might also be useful as merely an error message add on.