Fix race condition with Order creation.
Improvements for anonymous order.
Merge branch 'master' into cart-order-improvements

Conflicts:
	apps/fund/views.py
Add order creation to a critical section to avoid dup. orders.
Merge branch 'master' into cart-order-improvements
Remove session_key from Order model.
Cleanup imports.
Fixes from review with Loek.
Merge branch 'master' into cart-order-improvements

Conflicts:
	apps/fund/views.py
Merge pull request #200 from onepercentclub/cart-order-improvements

Cart order improvements