Add livereload options

To use this feature, just add livereload options. They're pretty much directly aped from the base fork, so see [its documentation](https://github.com/gruntjs/grunt-contrib-watch#optionslivereload) for the gist 

Also note that because of how this branch operates on all tasks at once, there's no target-level config support for livereload. That means you **must** define a single livereload option at the top of your `watch` config like so:

```
    watch: {
      options: {
        livereload: true
      }
```

Proof of life:
![livereload](https://cloud.githubusercontent.com/assets/79303/3351921/020ad1ee-fa26-11e3-8277-6fa1154e054e.gif)