Collections

This adds collections to the mix.

## Creating a Collection

Collections live under the directory named `collections` in your roms path. Add a directory with the name of your collection under it. Add an `image.png` art file, and the collection will be available in Kart.

```
/roms
  /collections
    /The Legend of Zelda
      /image.png
```

Once your collection is available, you can add games to it. See the gif below on how to do that.

![collections](https://cloud.githubusercontent.com/assets/260/3554322/cdb6b92c-090b-11e4-9d0c-73df91f2fb03.gif)

## Caveats

Collections are not browsable yet, lol. We need to create the new home screen before that's possible. I just want get this in there first before we go and change a TON of other stuff.