Add option to remove blank lines from output

[ezrafree]

Hello,

Allow me to begin by expressing my gratitude for the existence of this grunt plugin. Of all those I've tried this is the only one that I've been able to use to automatically format (or, "prettify") my Sass code.

I've modified prettysass.js a bit to add an option to remove blank lines from the output.

Here's my modified version of prettysass.js:

http://websightdesigns.com/prettysass.txt

Just let me know if there's anything I need to do on my end to commit this into the repository.