Changed visibility from a string 'morning'/'evening' to enum type.
Was not testing visibility was correct; now test.py does that.
Corrected a couple of minor things in C documentation.
Will generate different Markdown for my regular classes,
enumerated types, and error types.
Found out that 'from enum import IntEnum' pulls IntEnum
into the astronomy module and causes us to try to generate
documentation for it. Just keep it in the enum module.
Removed spurious dump of JavaScript README.md when verify_clean
fails.
I'm not going to use type annotations in function signatures
because they are causing more problems than they are worth.
The last straw was that different versions of Python don't
generate the same text representation. This broke my Travis CI
tests.
