Mention PyPI in the readme.
Fiddle around with documentation.
Improve handling of funky request paths.

  - When running requests, prepend a forward-slash to request paths that
    lack a trailing forward-slash.
  - Write a test for trailing-forward-slash-lacking request paths.
Improve "nfsnapi.auth_header()".

  - Prepend a forward-slash to request paths that lack a trailing
    forward-slash.