This fixes the lightbox zoom issues that occurred on some browsers
due to the units of `deltaY` being in lines rathern than pixels,
making it incredibly slow to zoom.
This makes the canvas zoom and pan feature cross-browser compatible in
a few ways:
1. Replace deprecated `mousewheel` event in favor of the similar and
cross-browser event `wheel`.
2. Create approximate substitute for `e.movementX` and `e.movementY`
values that are missing in Safari.
Tim Abbott
Brock Whittaker