VRFS-1577 VRFS-736 added should_rate_session?; fixed bug in add_rating

ruby/lib/jam_ruby/models/music_session_user_history.rb

@@ -105,10 +105,15 @@ module JamRuby
     def add_rating(rval, comment='')
       rval = rval.to_i
       if 0 != rval 
-        self.rating += rval
+        self.rating = self.rating.to_i + rval
         self.rating_comment = comment
       end
     end
 
+    def should_rate_session?
+      2 <= music_session_history.unique_users.count && 
+        60 < (Time.now - music_session_history.created_at).seconds
+    end
+
   end
 end