Missed one case where 'tag' should have been 'tags' in
58efeab3. Also updated same thing
in documentation.

Fixing issue where some float fields were left as strings in
LVAlert JSONs and response JSONs.  Occurred because they were
extracted as strings from files and saving the event did not
fix the attribute types without refreshing from the database.
See https://git.ligo.org/lscsoft/gracedb/issues/10.

simplejson package is used to properly serialize Decimal objects
(like gpstime) when converting from a dictionary to a json.

Event time nanoseconds did not include leading zeros when printed
in event.log (since 2010!!). See
https://git.ligo.org/lscsoft/gracedb/issues/9.

adding optional override to Event delete() method which removes data directory and all associated GroupObjectPermission objects