Compatibility with Grunt 0.4.x

Hi Ronald. As the registerHelper method is now deprecated, I've refactored the code to be compatible with Grunt 0.4 by rewriting the helper similar to this: https://github.com/cowboy/grunt/commit/d952a25db4a750571a5303ed603145ab80dddacb

grunt.utils was also changed to grunt.util, and I've updated to be compatible with both 0.4.x and 0.3.x.

Cheers,

Loyal