lessphp support

a lessphp port to minify, i've taken somebody else's work and rebased it to current master

overall expression: a group with single .less file: worked

@mrclay: could you drop your guidelines how to improve and make this work as you would intend?

Which library are we talking about? If it's the old stuff I worked on 4 years ago, I'm not sure if it should be reused anymore :-)