Option to add a suffix to the fingerprinted filenames

We're moving bustle.com from the Rails asset pipeline to the ember-cli. Our assets are heavily cached by our CDN. If we make any changes to our asset compilation we get stuck with stale files in our CDN. We've also run into scenarios where we needed to change headers or Content-Type in our CDN. By adding a suffix to the file name, this gives us an interface to force our assets to change. The only way to accomplish this otherwise was to manually make a change to the asset that forces the fingerprint to change.