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 over the weekend 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.