Produces a custom output format function in the style of Edward Tufte's handouts. This
essentially recreates the tufte-handout latex document class using bootstrap.
Main features are plot hooks that put figures in the margin (marginfigure = TRUE),
creates full-width figures (fig.star = TRUE), and allows "sidenotes". To create a sidenote,
some raw html is required. Usage is <aside> Content </aside>. See the
package vignette for more details.