Multiple modifier keys will not bind to 'keyup'

[prominentdetail]

For example:
mousetrap.bind('ctrl+alt', bindUp, 'keyup');
or
mousetrap.bind('shift+space', bindUp, 'keyup');
..will not fire when those are released.
Any help solving this would be appreciated, or direction towards where in the code this type of thing is handled so that I can try fixing it.

[robincafolla]

Testcase: http://jsfiddle.net/08moucLg/1/

Works for 'shift+space' but not for 'ctrl+alt'

[prominentdetail]

ah.. yea I checked again and seems space works..
But any combination of ctrl,alt,shift, and meta won't trigger a keyup.

[prominentdetail]

Okay, I created a pull request to show a fix I've made for this problem: #317