Plus reorganise tests

Validation is based on wikipedia list of postal codes [1]. Formats were
converted into regexes for countries.

1: http://en.wikipedia.org/wiki/List_of_postal_codes

Fixes #753

Fixes #745

Bad index in `last_line = covered_lines[-1][1]` (previously [-1][0])
caused rounding error. When you have 3 products for £7 and benefit 3
things per £20, each product would get discount £0.33 which doesn't sum
up to £1. The existing code handles this but bad indexing makes it fail.
A test case reproducing the issue was added.

Fixes #742

It's not really needed as it doesn't make sense to simply add an address
to your addressbook as part of checkout.

This change adds a uniqueness constraint on user addresses to prevent
duplicates.  A few changes follow:

- The user address forms in account and checkout are modified to take a
  user as a constructor arg so uniqueness can be checked.

- The assignment of a user when creating a new address has been moved
  into the form.

Also I moved the generate_hash fn up to the Address superclass as it's
possible that it might be used in other Address classes.

Caused by reworking of the user creation form.

I used the existing script [1] that cooperates very nicely with vim.
1: https://github.com/rory/django-template-i18n-lint

Fixes #676

- Use a FormView (as it is a form view)
- Move the redirect URL validation into the form

The backported version didn't explicitly create the ProductAttribute
instances before assigning and so they didn't save.

If parent is given, only parent descendant categories will be returned.

Fixes #741

- Add more links
- Add event details to line detail page

Fields now more self-contained, the bankcard form is much simpler.

This makes creating simple shipping repositories simpler as you only
need to override the methods attribute.

This allows updating code in both places, if necessary. Getting Django
1.5 support would be painful otherwise. This also removes the circular
dependency of django-oscar-testsupport on Oscar.

The requirements were merged. The imports were updated
accordingly. Unused imports in the touched files were removed. No
further changes.

* Emailbackend: Updated to use REQUIRED_FIELDS
* Demo and sandbox site now use compat.AUTH_USER_MODEL as well
* Added example custom user that gets tested for Django >= 1.5

This is required to allow the pages component of the dashboard to
continue to work correctly.

* Tidy implementation of validator
* Tests improved and moved to tests/integration (as they call resolve
  internally)

Change to required address fields was causing the shipping address step
to fail.

When adding to the basket, products with options were treated as
different products for each combination of options. This allowed adding
more products into the basket than are available for purchase.

The handling has been updated to sum up the already added quantity of
the product regardless of options.

Fixes #665

This is required for multiprocess testing to work (eg ./runtests.py
--processes=2)

Fixes #614

As they save stuff...

We now check in the OrderCreator for this attribute and only allocate if
it is true.

Fixes #671

Without a value, applying an AbsoluteBenefit raises a TypeError.

Fixes #670