respect DOM re-ordering of formsets even if the parent form errored
Added assertRegex to WagtailTestUtils
Added failing test for #222
Merge remote-tracking branch 'nimasmi/DOM_formset_reordering' into issue/222
Fixed a few errors in edit handlers tests
Tweaked reordering test to use InlinePanel children rather than its formset
Merge pull request #425 from kaedroho/issue/222

Fixes and Tests for #339