Fix several issues for Django 1.6
Adjust version dependencies for Django 1.6
Disable template timings toolbar panel
Add migration for NullBoolean field
Offer wizard works with JSON session serializer
Add reordering products inside ranges
Fix PEP8
Clean range ordering

- Remove forgotten print statement
- Rename `RangeOrdering` to more generic `RangeProduct` (later we can
  add another fields that are not ordering specific)
- Use `display_order` rather than priority (we set the order using
  jQuery sortable, not bump priority of couple products)
Fix backwards incompatible changes
Add correct CSS for date picker

It was using a incomplete bootstrap-datepicker.css. I couldn't find a
better suited replacement, so just switched to an okay looking JQuery UI
theme.

Also switched to the minified version of JQuery UI.
Upgrade timepicker to current version

As part of reviewing datetime pickers, it seemed sensible to bump to the
current version.
Reduce number of evaluated queries.

* Replace "foo.count() == 0" with "not foo.exists()" in python files
* Replace "foo.count() > 0" with "foo.exists()" in python files
* Replace "{% if foo.count %}{% for bar in foo %}" with
  "{% if foo %}{% for bar in foo %}"
* Use 'with' template tag in templates
* Add myself to AUTHORS list
Reduce number of evaluated queries.

* Properly close with tag.
* Properly check for band existance
Add note to release doc on Django 1.6 support
Merge pull request #916

Conflicts:
	.travis.yml
	requirements.txt
	tox.ini
Reduce number of evaluated queries.

Use 'for..empty' templatetag
Don't use |length filter if not reqired
Remove unnec. templates

Now superceded by changes in master.
Modernise requirements files

Bring package version up to date.
Serve tracker pixel from Tangent's infrastructure

This is to enable some coarse metrics of who is using Oscar.  We just
look at the referer header to get a rough idea of which sites are using
Oscar.

This is an important measure for Tangent, Oscar's sponsor.  It's
documented in the release notes and we'll make sure everyone knows when
Oscar is released.  It's easy to opt out of.

Fixes #656
Adjust migration to handle data changing part specially

I can't recreate the original issue but, according to a comment by
@vdboor, this change should ensure that the date migration does not
conflict with the schema migration.

Going forwards, I will ensure migrations don't mix data and schema
changes but at this point, it seems better to adjust this migration
rather than renumber (which causes problems for anyone who has already
applied this migration).

Fixes #977 (hopefully)