Can `rel="stylesheet"` be included by default?

[SimonEast]

Amazing plugin. Was searching for something to do exactly this: concatenate, minify and compile LESS/SCSS (without precompilers). But have come across a few possible improvements which I'll post as separate issues.

Firstly: is there a reason that rel="stylesheet" is not output by default when compiling CSS/LESS/SCSS? If the source files are compiled, I can't think of a situation where you would not want this included. Currently you have to specify this attribute every time you call the filter.

Happy to submit a pull-request if there's no major roadblocks to this.