Livescript support

[activestylus]

When I follow the instructions in the README, my file successfully concatenates other livescript files. It fails to require any js files I include

``
//= require vendor/jquery.js
``
#=require require/thing.ls

As you can see I am using double backticks, which is livescript's equivalent to inline js in coffeescript. In the resulting javascript all I get is

//= require vendor/jquery.js
// ....my app code here

Instead of concatenating the file contents the comment stays intact