CHANGES IN tufte VERSION 0.3 (unreleased)

NEW FEATURES

It is possible to select a subset of some features of the default Tufte style (tufte-css) via the tufte_features argument of tufte_html(). For example, you can disable the et-book fonts and the background color.
A new variant of the Tufte style, envisioned, is added to tufte_html(). You can use tufte_html(tufte_variant = 'envisioned') to enable this style. The major difference with the default Tufte style is: the font family is Roboto Condensed, the background color is #fefefe, and the text color is #222 (thanks, @eddelbuettel, #21).

when link-citations: no in YAML, citations should not be moved into the page margin in the HTML output (http://stackoverflow.com/q/39053097/559676)
horizontal lines could bisect margin notes and footnotes (thanks, @ajdamico, #32)

it is possible to generate PDF output using the ctex package for R Markdown documents in Chinese; you just need to specify ctex: yes in the YAML metadata

the default LaTeX template for tufte_handout() may not work when the LaTeX package soul is installed, or ifxetex/xltxtra are not installed
the number_sections option did not work for LaTeX output

added three output formats for R Markdown: tufte_html(), tufte_handout(), and tufte_book()