Added a slide demonstrating that nested reveals are somewhat sane. Modified lists so every element but the first has some room above it.
Simplified the logic by taking advantage of chained selectors.
Avoided repeating some code
Messy commit; halfway through re-working the object model.

TODO: Develop an object for each slide. This object should have a
reference to a d3.selection containing the appropriate DOM subtree to
allow for manipulation, along with tracking which stages are displayed.
Merge branch 'events' of ssh://bitbucket.org/prsteele/html-slides into prsteele-bitbucket-event
Moved to a saner, object-based system for handling slides. There is a
Slideshow object which contains all slides on the page, and handles
transitions between them. Each slide is represented as a Slide object,
which knows how to display itself on screen as well as its stages.