find replacement for django-jsonfield

[jamesturk]

if we want Postgres' JSON we may want to move away, this is a known issue. rpkilby/jsonfield#80

for now I've pinned the jsonfield version to 0.9.20 which doesn't have a problem, but we're getting weird errors on 0.9.22 (on travis) where the JSONField comes back as '{}' instead of {}

[jamesturk]

honestly everything is working, so this may be a Django 1.8 kind of thing

[paultag]

Yeah, I'm thinking jsonb is the way to go here; let's break out once we can land 9.4 and have a solid route to use it.

Also, wow, this was the bug we were seeing not to long ago, cc @boblannon

[jamesturk]

closing this as Django 1.9 fixes this in 0.7