LM #20 Sender not Recipient message validation

Created spec for model to test validations
LM #20 - Fix sender/recipient relation
LM #20 #17 - Require 1+ recipient. Improve localization
#20 - Remove model logic from routing test
LM #20 Update user fixture initial lowercase
LM #20 make message valid for message controller
LM #20 Identify/reject unknown sender/recipient
LM #16 - validate message has sender(s)
LM #18 - Validate message has non-tags