Slide notes are now served correctly (as application/xhtml+xml) to compatible
browsers. So you can put math in your notes, and the MathML will render.
We don't do real content-negotioation. IE gets text/html; everyone else gets application/xhtml+xml.
Added support for S5 Themes. Themes are stored in the public/s5/themes/ directory.
6 themes are included: default, nautilus, blue, flower, i18n, pixel.