Add to README a note on the use of callback macros and limitations with respect to inheritance when associations are set up before validates_constancy_of is called (see "IMPORTANT" under "Inheritable callback queues" in http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html)
Add to README a note on the use of callback macros and limitations with respect to inheritance when associations are set up before validates_constancy_of is called (see "IMPORTANT" under "Inheritable callback queues" in http://api.rubyonrails.org/classes/ActiveRecord/Callbacks.html)

njonsson/validates_constancy