Adding a template_context keyword to allow passing of fields to templates.
The AutoIndex class and render_autoindex method now take an extra keyword argument ``template_context`` whose contents are passed to ``render_template``.  This allows custom templates to get extra fields so they can inherit from and work with other templates in the application.
Merge pull request #8 from rptb1/add-template-context

Adding a template_context keyword to allow passing of fields to templates