Updating grunt-link to work with Grunt 0.4

+ updated to new batched alias syntax (array instead of a string)
+ Renemed grunt.js to Gruntfile.js
+ Added Grunt 0.4 as a dev dependency
+ grunt.utils has been renamed to grunt.util
+ grunt.file.expandDirs has been dropped in favor of grunt.utils.expand
+ added grunt-cli as a before dependency
+ removed Node 0.6 support
Merge pull request #1 from nicknisi/grunt-4-update

Updating grunt-link to work with Grunt 0.4