Older date filtering on pubs and announcements lists

https://www.pivotaltracker.com/story/show/48642641
Change date select options to alway start on 2010-05-01
Fix spec for timecop date set
Fix start_index in Worlwide API responses.

This was returning page_number * page_size, which is incorrect as
pace_number starts at 1.
Merge pull request #521 from alphagov/fix_ww_api_start_index

Fix start_index in Worlwide API responses.

https://www.pivotaltracker.com/story/show/48397943
Merge pull request #490 from alphagov/increase-the-date-of-filter

Older date filtering on pubs and announcements lists

https://www.pivotaltracker.com/story/show/48642641