Added LESS compilation as an option

With this, you can now change

`grunt.registerTask("default", ["steroids-make", "steroids-compile-sass"]);`

to

`grunt.registerTask("default", ["steroids-make", "steroids-compile-less"]);`

in a project's `Gruntfile.js` to compile LESS files in the same manner that Steroids currently compiles SASS files.