Fix #105: Improve documentation and add more logging.
Fix minor nits

* tweak get_audience docstring for clarity
* change log to logger, nix .format() calls
* tweak site_url checking
* invert SANITY_CHECKS setting: Peter likes False by default, so this
  inverts the name and value.
* move sanity_checks to base for reusability
Fix notty typo
Merge pull request #122 from willkg/less-pain

Less pain