Update to grunt 0.4, and node 0.10 GH-6

So I don't have push access to the original repo.  But this should be for issue 6: https://github.com/concordusapps/grunt-haml/issues/6

I had a concern though, we were using `helpers.options` in the task.  Is that necessary for something?  It seems that `this.options` provides the task with the options defined in `Gruntfile.js`.  Or is there something else that is going on?  I removed the dependency for `grunt-lib-contrib` if we don't need that helper anymore.  If so, I can add that back in.  I also tried to clean up the transpile function a bit, so that it is easier to read and maintain.  Hopefully that should make adding additional languages easier.

Updated to node 0.10.x.  The tests pass on my machine with `npm test`, dunno about travis yet though.