Added support for SASL authentication in MemcachedCache, fixed FormParser bug, added support for python-binary-memcached

Support Additions:
- Memcached SASL auth
- Python binary memcached library

Bug fixes:
- Modified a FormParser test that was failing on account of a bad assertion
I think this should be ``if``, not ``elif``. Otherwise you might actually end up with a string if you pass ``None``,