More stuff can be bold.
Better bold support.
Add a buttload of new tests.

Also added a script to regenerate all of the test output files; this
should only be used when a major change to our output format
occurs (e.g., when we support wrapping our LIs in ULs.)
Ignore more transformations while inside `code' blocks.

Prompted by writing a page in markup and trying to include examples of
the markup in the page, which broke it. Works now, yay!
We should be able to have monospaced asterisks.
Process simple external links kurrectly.
Add test for simple external links.
Update TODO.