Fixed ZeroDivisionError in fill filter

When a focal point matches the size of the image, the crop sizes are
also the same.

These sizes are subtracted from each other in the fill filter
(which would equal zero) and this number then gets used as the
denominator in a division causing the ZeroDivisionError to be raised.

The fix is simple, don't do any crop closeness calculations if the focal
point size equals the image size. Crop closeness wouldn't work anyway in
this case
Created failing test for #798
Use DjangoJSONEncoder for encoding form submission

Fixes #798
Create changelog / release notes section for 0.8.2
Various fixes to Elasticsearch configuration

- It's now possible to specify http auth paramters in the URL
- I've changed the default port to 443 to SSL connections and 80 for
  non-SSL connections. Previously, both were set to 9200.
Merge branch 'fix-form-submission-encoding' of https://github.com/kaedroho/wagtail into kaedroho-fix-form-submission-encoding
Release note for #799
Merge branch 'kaedroho-fix-form-submission-encoding' into stable/0.8.x
Merge branch 'fix-fill-filter-zerodivisionerror' of https://github.com/kaedroho/wagtail into kaedroho-fix-fill-filter-zerodivisionerror
release note for #797
Merge branch 'kaedroho-fix-fill-filter-zerodivisionerror' into stable/0.8.x
Merge branch 'issue-786' of https://github.com/kaedroho/wagtail into kaedroho-issue-786
Release notes for #802
Merge branch 'kaedroho-issue-786' into stable/0.8.x
Change 'Field hasn't specified on_delete action' to a warning rather than an error, as per #792
release note for 35b8bc2
add missing south migration - remove auto_add_now from page_revision.created_at and nullify page owner on user deletion
add migration to tests app to fix typo in formfield help text. (Most. Pointless. Migration. Ever.)
Add dependency on wagtailcore migration 0002 (necessary to cleanly merge the other migration 0005 being added in 0.9)
Fix some more python3.2-incompatible unicode strings in migration 11