NPM module-ize CAH so it can be loaded as an external

This PR :package:s it up so it can be added to Hubot without copying/pasting and tracks future updates. Would be good to send this part upstream to @jonnycampbell so it can be loaded by adding this to the configuration:

`package.json`
```js
    "hubot-against-humanity": "jonnycampbell/hubot-against-humanity"
```

`external-scripts.json`
```js
["hubot-against-humanity"]
```