Allow hidden files (starting with '.') to be shown in indexes.
Add the keyword parameter "show_hidden" to both AutoIndex init and render_autoindex methods, with the former providing a default for the latter.  The logic was already there in the "explore" but had not been plumbed through to the external interface.
Merge pull request #10 from rptb1/show-hidden

Allow hidden files (starting with '.') to be shown in indexes.