rename component.json to bower.json

When I use [bower][] to install [toc][] as a dependency the following warning is issued.

```shell
bower warn Package toc is still using the deprecated "component.json" file
```

As detailed in the *Defining a Package* of the [Bower README][readme] the use of `component.json` is deprecated in favor of 'bower.json'. This pull request renamed the `component.json` to the preferred `bower.json`.

[bower]: http://bower.io/
[toc]: http://projects.jga.me/toc/
[readme]: https://github.com/bower/bower/blob/master/README.md#defining-a-package