Added loading of JSHint config

Hey,

I've noticed that this feature was missing (https://github.com/addyosmani/sublime-fixmyjs/issues/2) and I really needed this feature, so i did my best and implemented it.
If it needs more polishing, just say :-)
```js
var config = opts.filepath && jshintCli.getConfig(opts.filepath) || {};
```