Add a TODO comment in config/models re:json.
Add a TODO comment in config/models re:json.

See gh-13.

Turns out that adding "json" could give us ToJSON and FromJSON
instances of record types in config/models.  But BloodGlucoseHistory
isn't eligible because of our homespun BGUnit member.  Maybe take
another look at this, later.

sajith/betty-web