Included broccoli-asset-rev for fingerprinting in EmberApp

This is a WIP.

I have included https://github.com/rickharrison/broccoli-asset-rev to both fingerprint files as well as replace them in the source. This will turn:

`<script src="assets/appname.js"></script>`

into

`<script src="assets/appname-ce5adb2fb916f0fdaa16c282dd074239.js"></script>`

I added an option to EmberApp to pass options for excluding files to be fingerprinted. `EmberApp.options.fingerprint.exclude` should be an array of strings, which if any file contains any string in that array, it will not be fingerprinted. As an example, I do not fingerprint my typography.com stylesheets:

```
var app = new EmberApp({
  name: require('./package.json').name,

  minifyCSS: {
    enabled: true,
    options: {}
  },

  fingerprint: {
    exclude: ['fonts/169929']
  },

  getEnvJSON: require('./config/environment')
});
```

Currently, I am working on an option to prepend a string to all of the fingerprinted files in your source for a CDN like cloudfront. Currently, it works great for `index.html` with your css and js assets. The only thing I have left to work out is what to do in css files when you have `../` or `/` in front of the filenames. Right now, it would end up like this:

`background: url('../https://abcdabcd.cloudfront.net/images/foo.png');`

Let me know what you think and I can improve upon it!