update vis.js to fix scaling issues for ios safari mobile

[nfischer]

We have special code to disable zooming on mobile:

framily-tree/index.html

Lines 6 to 7 in 61c6de1

	<!-- Disable zoom on mobile -->
	<meta content='width=device-width,initial-scale=1.0, maximum-scale=1.0, user-scalable=0' name='viewport'/>

However, apple decided to disregard this on iOS 10.

It looks like this issue was fixed upstream in almende/vis#2123, so we should update the dependency and see if it fixes the issue. After that, we should see if we can remove the user-scalable stuff.