changed logging to use named logger.
added more file documentation
spelling correction
list_tags now returns a list of tag names.
It used to return a list of {'name':'tagname'} dicts. now just returns the tagnames.

Also cleaned up documentation a bit.
get_person_by_email() now returns None instead of raising exception if not found.

Similarly get_id_by_email.
added match_person() for general matching.
cleaned docs a little bit
Moved tag-related
moved tag-related stuff to tags.py