use latest require-less to get less.js 1.5.0.

Bug in earler 1.4.2 breaks firefox.
Merge remote-tracking branch 'origin/master' into firefox-fixes
Configure less.js to dereference relative urls to the file it's in.

This is required for less.js 1.5.0, which in turn is needed to get this working
in firefox. It has to be set very early. Setting it in config.coffee seems
to be too late.
Account for the 1px borders on the sidebars.

Firefox is more strict about this. If you're off by these two pixels, the
editor is pushed off the screen and cannot be reached.
Mozilla specific width styling for ff < v16.
Merge pull request #116 from oerpub/firefox-fixes

Firefox fixes