Add more events from gaze

It is useful to have more events being re-emitted from [gaze](https://github.com/shama/gaze#events), like `added` and `deleted`. For example, I want some pipe actions to be performed only when a file is added, and I'd like to have this event to be triggered in gulp code:

```javascript
watch({glob: '**/*.js'})
  .on('added', function (file) {
    // file is added
  })
  .pipe(gulp.dest('dist'));
```