v0.4.0

• Improved preprocessing for siunitx notation, LaTeX math, and HTML comments.
  Fixed catastrophic backtracking in LaTeX math regex (#11). Added support
  for newlines in HTML comments. The preprocessor now skips backslash
  escapes, inline code containing newlines, and fenced code blocks (as long as
  they do not start on the same line as a list marker). The preprocessor now
  handles the escape \$ itself, since Python-Markdown ignores it (#14).
• Python-Markdown's Markdown-in-HTML extension is now enabled (#13).
• Added quiz options Shuffle answers, Show correct answers,
  One question at a time, and Can't go back (#10). These options are
  apparently ignored by Canvas, but may work with some other systems.
• Revised README to clarify that some features are apparently not supported
  by Canvas (#16).