Fixes #97 - cache updated cart items in cart object.

Avoid code duplication and unecessary db queries.
fixes #102 do not rewrite product name in OrderItem
Added changelog for latest changes
Merge branch 'fix-102-no-re-set-product-name' of https://github.com/bmihelac/django-shop into bmihelac-fix-102-no-re-set-product-name
Added changelog entry for various bugfixes (including #102)
Using a dynamically generated form for cart view in order to validate input.
Added .ropeproject to .gitignore.
New approach with modelformset.
Removed unnecessary form fields iteration from cart.html
Making existing tests work again: Adding management_form data to test's POST data.
Added tests for new modelformset code. Fixed some PEP8 errors. Fixed some failing tests.
Added description of new formset usage to CHANGELOG.rst
Merge pull request #114 from mbrochh/cart_form

Using a dynamically generated form for cart view in order to validate user input. This will break your cart.html template. Please see CHANGELOG for more details.
Set max value on cart item form.
Huge PEP8 cleanup.
Merge pull request #116 from mbrochh/pep8_cleanup

Huge PEP8 cleanup.
Merge pull request #115 from mbrochh/form_max_value

Set max value on cart item form.
work arround avoids circular importation via load_class by extrapolating the app_label and model name from the class_path.
a more comprehensive solution to the circular import problem; also, allowing cart update to accept data from GET as well as POST.
Added documentation on how to properly send code

Since we have had so many pull requests from master branches, here is a little
more documentation on how to submit your code.