Additional custom html writer changes

[QuLogic]

This fixes a few things that I've run into so far.

[ryan-roemer]

@russell -- Can you shepherd this PR when you get a chance? I'm not that up to speed on the custom-html-writer branch... Thanks!

[ryan-roemer]

@QuLogic @russell -- If you get a chance, here's an email I got from @rougier about a "Bootstrap RST" project he's been working on in case that helps this effort!

Thank you very much for the sphinx bootstrap theme. I've managed to make a "modern" site (with some html hacks).

http://glumpy.github.io/

I've also been playing with bootstrap with regular RST (to avoid html hacks):

http://rougier.github.io/bootstrap-rst/ https://github.com/rougier/bootstrap-rst

Could be useful as an external writer for the bootstrap theme (maybe).>