Customer.sync Issue

Fixing bug where credit card does not get removed properly.  Also fixing issue with signal card_changed not getting sent when there is a card change whether it be removed or updated.

All of these fixes include tests.
Spelling error - also see this for how to patch settings in Django:

https://docs.djangoproject.com/en/1.5/topics/testing/overview/#overriding-settings
Merge branch 'master' of github.com:eldarion/django-stripe-payments into bug/credit-card-updates
Fixing line too long lint error - LAME ;)
Another lint bug: E125 continuation line does not distinguish itself from next logical line
Fixing spelling mistakes
Changing the disconnect / connect signal handlers to not use weak references
Merge branch 'master' of github.com:eldarion/django-stripe-payments into bug/credit-card-updates

Conflicts:
	payments/tests/test_commands.py
	payments/tests/test_customer.py
	payments/tests/test_email.py
Formatting and lint fixes
Merge pull request #94 from fredpalmer/bug/credit-card-updates

Customer.sync Fix for Removing Credit Card