Nullable MoneyField should act as default=None
Fixed bug where a non-required MoneyField threw an exception.

To be precise: InvalidOperation: Invalid literal for Decimal: 'None'
Fixed issue with Form.changed_data always including MoneyFields.

This is a particular issue for empty inlines in Django admin, which
the admin thinks are not empty because of the previous behaviour.
Added "choices=" to instantiation of currency widget

This prevents a "list has no attribute copy()" error when using the MoneyWidget directly in a form definition
Merge pull request #92 from davidstockwell/master

Added "choices=" to instantiation of currency widget
Merge pull request #83 from spookylukey/null_default_for_nullable_field

Nullable MoneyField should act as default=None
fix merge conflict
Merge branch 'spookylukey-fix_form_validation_for_optional_moneyfields'
Merge remote-tracking branch 'upstream/master'