Django 1.7 support

[littlepea]

With Django==1.7.2 the following Warnings show up when running ./manage.py validate:

System check identified some issues:

WARNINGS:
billing.PinCharge.success: (1_6.W002) BooleanField does not have a default value.
    HINT: Django 1.6 changed the default value of BooleanField from False to None. See https://docs.djangoproject.com/en/1.6/ref/models/fields/#booleanfield for more information.
billing.PinRefund.success: (1_6.W002) BooleanField does not have a default value.
    HINT: Django 1.6 changed the default value of BooleanField from False to None. See https://docs.djangoproject.com/en/1.6/ref/models/fields/#booleanfield for more information.

System check identified 2 issues (0 silenced).

[theju]

The past few commits have been to support django 1.7. Please let us know if they are working fine on your end.

[theju]

Closing this as it seems to be working fine with django 1.7. Please feel free to reopen the ticket if not so.