Mouse events are extremely expensive on Firefox 25

[rustinlee]

Someone else brought this to my attention because until now I've only tested the game on Chrome, but it appears that repeatedly clicking on the canvas in the latest Firefox causes immense slowdowns. CPU profiling confirmed the issue:

Issue does not occur in latest Chrome. Using latest version of createjs from the official CDN, unsure as of yet if the issue is with my implementation of mouse events (with help from jQuery) or with createjs itself. Profiling CPU usage using the demos at http://www.createjs.com/tutorials/Mouse%20Interaction/ again reports mouse events as the most expensive but nowhere near as bad as in my game.

[rustinlee]

Issue fixed @ https://github.com/rustinlee/armipotent/commit/9d28289db9039ed26f218de02d376f5f1c31de5b

Still, strange that only Firefox has this problem. Might let the people at CreateJS know.