Docbook template:  Use docbook 5.5.  Closes #25.
LaTeX template:  Changes to make mathfont work with xelatex.

We need the mathspec library, not just fontspec, for this.
We also need to set options for setmathfont.
revealjs template: use remotes by default, set defaults from query hash.
Fixed errors introduced in last revealjs template update.
default.latex: Redefine includegraphics to allow custom options.

Thanks to Bernhard Weichel.
Now, literal \includegraphics commands with square-bracketed options
will work properly.  When no options are given, a default option
limits images to the text width.
default.latex:  Use \ScaleIfNeeded w/ nicer def instead of \maxwidth.
default.beamer:  Added comment to graphics section.
Add class attribute to title slide section tag

It would be useful to have a class attribute for the title slide's section tag. For example, this is useful for setting a background image unique to the title slide.
Merge pull request #29 from abakst/patch-1

Add class attribute to title slide section tag