Minor code tweaks

Changed bracket style to "K&R" or "egyptian" as it is a more widely accepted convention for JavaScript (hope it's not critical :grin: ).

`this.data` is deprecated and `this.options` is a more flexible way to access task configuration in Grunt. (See [this](http://gruntjs.com/api/inside-tasks))

`typeof f === "function"` is a safe enough way of checking whether a variable is actually a function, it's in the standard and doesn't have any misdetection cases ([a related question on SO](http://stackoverflow.com/questions/17108122/isfunctiona-vs-typeof-a-function-javascript)). Furthermore, `grunt.util._ ` is [deprecated](http://gruntjs.com/api/grunt.util).

That's it, I guess :sweat_smile: 

See each commit diff for more details.