Normalize license header appears multiple times even in `compressed` output

[benknight]

I just thought I'd point out that when compiling in compressed output mode, this Normalize header gets repeated over and over again, since it starts with a /*!:

/*! normalize.css v3.0.0 | MIT License | git.io/normalize */

9 times actually, one for each scss partial in this repo.

It should probably only need to be there once since the idea of compressed mode is to shrink the file as much as possible.