Switch from sass to stylus

Addresses issue #100.

Switch from compass + sass to stylus + nib.  Stylus syntax is almost identical to SCSS.  The only differences pertinent to what we had is that it's strict with white-space, and uses " = " for variable assignment instead of ": ".

This PR uses the connect middleware strategy for compilation that intercepts all ".css" requests and looks for an associated ".styl" file to compile as needed.  If we ever got real for-serious traffic such that static were a bottleneck, we'd want to use a different strategy.

Also removing the unused "ie.css" and "print.css" files and hrefs that we weren't using (they're stubbed by compass).