Sanitize project names into valid url format

Update referencing feature request: chrismccord/labrador#17

I added a url_name method to the App class that sanitizes the project name into something more url friendly and valid. An example would be:

Labrador::App.url_name("Crazy Project Name") => 'crazy-project-name'

This allows you to use labrador with wacky projects such as "http://crazy-project-name.labrador.dev"

Take a look and let me know what you think about both the method and the naming rules/adjustments for projects.

Thanks!
David