JSON schema for coffeelint.json

Any editor/IDE supporting json-schema will be able to provide rich auto-completion for `coffeelint.json` files.

![completion](https://cloud.githubusercontent.com/assets/1258877/2715041/d4de18f0-c502-11e3-8737-d0dd90ecaa4e.png)

This makes it much easier to work with `coffeelint.json` files as well as helping to avoid typos. In addition, tooltips can be provided for easy explanations to each property.

![completion2](https://cloud.githubusercontent.com/assets/1258877/2715048/20c371d4-c503-11e3-8ccf-4e709a80dd97.png)

A json-schema file can also be used as documentation for the `coffeelint.json` file.