Added background_header_auto parameter that adds a
background under the first h1 element
(i.e. # Slide Title) on a slide. When enabled, the
background is added automatically to slides, as long as they aren’t
inverse, center, middle, or
bottom-styled slides. When disabled, you can still enable
slide title headers by adding the header_background class
to a slide. (thanks, @Btibert3, #10)
The underlying template now uses the whisker
package.