* Added support for images, using standard Markdown syntax.
* Added support for multi-paragraph descriptions, questions, choices, and
feedback.
* Added support for essay questions.
* Added support for numerical questions.
* Added support for question groups. A subset of the questions in a group is
chosen at random when a quiz is taken.
* Added support for executable code blocks. These can be used to generate
questions automatically. This feature requires the command-line flag
`--run-code-blocks` or setting `run_code_blocks = true` in the config
file.
* Quiz titles are now processed as plain text, rather than as Markdown,
because QTI does not support HTML titles.
* Fixed a bug that prevented source file names from appearing in error
messages. Fixed misspelling of "imsmanifest.xml" in QTI output.