Relax version restrictions for debug-toolbar plugins
Don't allow offer benefits unless tax is defined
Replace currency_filters with currency_tags
Ensure all templates specify a currency for prices

Apart from a few dashboard ones where there isn't necessarily one
currency to use.
Add decorator for ignoring DeprecationWarnings

Useful for testing functionality that is known to be deprecated.
Ignore expected deprecation warnings in test run
Remove currency_tags templatetag

The existing extension to the currency filter is sufficient.