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
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