def full_messages
      inject([]) do |m, kv|
        att, errors = *kv
        errors.each {|e| m << "#{e}"}
        m
      end
    end
def full_messages
      inject([]) do |m, kv|
        att, errors = *kv
        errors.each {|e| m << "#{e}"}
        m
      end
    end
Returns an array of fully-formatted error messages.

   errors.full_messages
   # => ['name is not valid',
   #     'hometown is not at least 2 letters']