Add gh-pages branch with documentation

The README keeps growing and there is more I'd like to add. This probably need splitting into multiple pages. A nodeunit site would be a useful place to share tutorials and API information for the less-simple stuff (custom reporters for example).

Start by reviewing the README and the documentation needs mentioned in the issue, including tutorials and API information for custom reporters. Determine the page structure and gh-pages publishing approach; done means the README content is split into a usable documentation site with the requested tutorial and API coverage.

Written by the indexing model from the issue text.