fix for using 'sass' css compressor

[ryankshaw]

running jammit using the 'sass' css compressor would fail because this method expects at least 2 arguments

see: http://sass-lang.com/docs/yardoc/Sass/SCSS/Parser.html#initialize-instance_method

since, at this point, it is just the combined input for all of the files in a bundle, there is no real filename i just called it 'jammit-combined-input'

[ryankshaw]

@jashkenas can you merge this? it's pretty simple and straightforward and makes it so using the sass compressor actually works.

[jashkenas]

Sure -- thanks.

[ryankshaw]

thanks