A few minor improvements/fixes

Zoom towards mouse position rather than origin.
Fix incorrect placement of new nodes when zoom != 1.
Reset max title width of output slots if the zoom level has changed. Previously the max width would incorrectly stay high if you zoomed in then out again.
Pan with middle mouse button rather than right mouse button since the right button is being used for context menu. Maybe the preferred fix would have been to not popup the context menu if panning had just completed.

rokups / ImNodes