TodoResource.convert_to_iso_format_with_milliseconds needs to be nicer
Issue #53
new
TodoResource.convert_to_iso_format_with_milliseconds
needs clean up and a direct test.
It should probably take a datetime instead of a ISO formatted string and shouldn't assume UTC (but honestly, the server is going to store everything in UTC forever since dates can get into an unmanageable state).
This came out of #52.