[READY] Set up sub-directories and routing

When navigating to:
`cell.dev/user/james`

Controller first checks whether an `index.php` exists within a directory first:
`cell.dev/user/james/index.php`

If not, it will then check whether a file with that name exists:
`cell.dev/user/james.php`

If not, it will 404.

This allows us to have readable URLs whilst also retaining a coherent file structure and the ability to have index pages.
- `cell.dev/user/james` - James' profile page
- `cell.dev/user/james/env` - List all James' cloned environments
- `cell.dev/user/james/env/1` - Detailed environment page for James' first environment

![BOOM](http://31.media.tumblr.com/baa6c4f749db7cac54a6449e3707d4b2/tumblr_myv2k6U5PE1qdlh1io1_400.gif)