Log Message:
Update to 0.19

Upstream changes:
0.19  2017-03-07
- Documentation:
-- "week_start_day" parameter no longer marked "for internal \ 
use".
-- Fix "week day" examples. Pointed out by Eric Jensen and Zefram
   in a thread started by Andrew Martin in datetime@perl.org
-- Clarify that week_start_day defaults to "1mo", except for
   yearly recurrences that default to "mo". Patches by David Steinbrunner.
-- Updated contact email.