Should be able to pass in the throttle time delay

[kennethormandy]

Needs a reasonable default set, I had 500 in the current version which is too short and causing problems on Mobile Safari and preventing parts of the page from rendering on quick scrolling. Bumping it up to 2000 seems to fix this, but should still investigate more and add a test if practical.

Edit The perils of using your own resize event, apparently: http://stackoverflow.com/a/29940941/864799