Put this plugin the plugin directory where it belongs.

The Brunch [docs seem to imply](https://github.com/brunch/brunch/blob/master/docs/config.md#overrides) there should be a `plugins` object where this stuff belongs. [Other plugins](https://github.com/brunch/coffee-script-brunch/blob/master/src/index.coffee#L25) adhere to this already.

Might be worth sprinkling some existential operators in there if you're worried about a `plugins` object not existing.