Use jingo.monkey if it exists

This changes funfactory to use jingo.monkey which monkey patches Django
form fields so you don't have to do |safe all the time.

If the available jingo isn't recent enough, then it defaults to using
nuggets safe_django_forms which don't appear to work with Django 1.5
or later.
Merge pull request #58 from willkg/jingo-monkey

Use jingo.monkey if it exists