Prelude docs

[gilch]

Whirlwind tour has now been trimmed to a reasonable length. The later sections demonstrating the usage of the bundled macros have been moved into the API docs, i.e., the docstrings of the macros themselves, although Sphinx is also rendering those.

This is most of #56, but I need to give all the docs a once over before the next release. There are still a few gaps and sections that should be rewritten.

[gilch]

This finally cleans up the half-baked "pardon our dust" section from #184