Update broccoli-asset-rev to latest version

I just tried to run the demo ember cli app in this repo and got the following error. Updating `broccoli-asset-rev` to the latest version seems to fix the issue.

```bash
$ node_modules/.bin/ember server
version: 0.0.37
The `EmberCLIAssetRev` addon must implement the `treeFor` hook.Error: The `EmberCLIAssetRev` addon must implement the `treeFor` hook.
    at EmberApp.<anonymous> (/Users/bmac/code/liquid-fire/node_modules/ember-cli/lib/broccoli/ember-app.js:122:13)
    at Array.map (native)
    at EmberApp.addonTreesFor (/Users/bmac/code/liquid-fire/node_modules/ember-cli/lib/broccoli/ember-app.js:120:40)
    at EmberApp.<anonymous> (/Users/bmac/code/liquid-fire/node_modules/ember-cli/lib/broccoli/ember-app.js:198:25)
    at EmberApp.memoized [as _processedAppTree] (/Users/bmac/code/liquid-fire/node_modules/ember-cli/node_modules/lodash-node/modern/functions/memoize.js:65:28)
...
```