new RelationalModel, supports direct composer object replacement in relations
a bit more abstraction as well as security updates: iv generations is truly random now (pending approval of tcrypts PRNG) and there is also a random_bytes function which is used by iv/random_key to provide random bytes to those functions. working nicely.
HACK in Conversation.refresh_personas: have to manually turn off encryption when upserting personas so key errors dont trigger. another option would have been to build/implement a Composer.Model.merge function...yuck. this works for now.

also, fixing timestamp generation in Message model