Add bower.json

## What this does
It would be great to be able to install mini.css via bower. That way everything a user has to to is typing
```bash
bower install mini.css
```
and he has the latest copy of mini.css installed.

---

## Actions after merging
This is the first step to making this project installable via bower.
After merging the `bower.json`, you have to push a tag 1.0.0 to the repository:

```bash
git tag 1.0.0
git push origin 1.0.0
```

and then [register](http://bower.io/docs/creating-packages/#register) it at the bower repository:
```bash
bower register mini.css https://github.com/elixir-web/mini.css.git
```
_(Assuming you have [bower installed](http://bower.io/#install-bower))_

---

## Notes:

- When doing changes to mini.css in the future, you will have to increase the version number in the bower.json and add a corresponding tag.

- You may have to edit the bower.json, if you which a different licence than MIT