Include the RSS file by default for the bs2 theme.
Include the sample configuration file.
Updated the way we mangle posts -> links.

We remove the suffix, which might not be ".txt", and rather than
blindly adding ".html" we add the configured suffix from the
configuration-file.
Added sample configuration-file.
Honour `index_filename`.

Some webservers might not like `index.html` and so we allow this
to be configured.