Allow for global prefixing

[erwstout]

For a few projects it was needed to prefix ginger to not conflict with existing class names in a project. Temporarily there is a simple repo created with a snapshot from 2.0.3 https://github.com/erwstout/prefixed-ginger

Could be interesting to explore a way to add a prefix to all the ginger classes - although I currently don't have a game plan of how to make this happen or when. Just a thought.