Add huxley options to gulp task

I was working on porting [grunt-huxley](//github.com/chenglou/grunt-huxley) over the weekend and didn't see your project. I'm hoping we can merge our projects together? I'm glad to see that someone else was working on this as well :smile: 

This fork lets you to customize the huxley options directly from your `gulpfile.js`.
```js
gulp.task( 'test', function() {
  gulp.src('test/**/Huxleyfile.json')
    .pipe( huxley( {
      root: __dirname,
      action: 'update',
      server: 'http://localhost:4444/wd/hub'
    } ) );
});
```
The gulp task also takes in the paths to the `Huxleyfile.json` files. It then grabs the directory names that those files are located in.