Demo breaks if you move over the sidebar

On the [default demo](http://jakiestfu.github.io/Snap.js/demo/apps/default.html#), if I start dragging the hamburger menu and move my pointer over the sidebar, the drag breaks. I'm guessing you're listening to `mousemove` on the wrong element or forgot to capture the pointer if you're using pointer events.

Incidentally, the [drag element](http://jakiestfu.github.io/Snap.js/demo/apps/dragElement.html) demo doesn't seem to have the same problem.

Reproduce the issue in the default demo by dragging the hamburger menu and moving the pointer over the sidebar; compare its behavior with the dragElement demo. Trace the default demo's drag handling to identify where movement stops, and consider the issue done when dragging continues across the sidebar without breaking.

Written by the indexing model from the issue text.