consider uaids/chids as opaque UUIDs

Don't convert them to binary for storage. We lose some storage
efficiency doing this, but impact less clients.
NOTE: this will render any current data stored in memcache to be
invalid or unfindable. clients will have to reregister after this patch
is applied.

Fixes #20 

@bbangert, @kitcambridge r?
:joy_cat: