Add memcached to Heroku

[banesullivan]

Leverage our recent support of memcached in RGD and hook it up to a new Memcached server on Heroku

[banesullivan]

Done in 3090ecf, dffc9cc, e3203fd

See also: https://github.com/girder/django-composed-configuration/issues/163

[banesullivan]

Having trouble. See DEBUG commits. The configuration sets this up but then it is reset to the default value of

>>> settings.CACHES
{'default': {'BACKEND': 'django.core.cache.backends.locmem.LocMemCache'}}

No idea why this is going awry. Though it looks like large-image working with it

[banesullivan]

It is currently added, but not working