autoResize calls $apply every 250ms

[KylePDavis]

Every time that ui.grid.autoResize polls for size changes it calls $apply (by way of $timeout). This can be very heavy on a site with a lot of watchers or complex $watch listeners.

At the very least I propose that we stop calling $apply as part of $timeout and call it explicitly instead. Even better yet I think that maybe we should only resize on $apply. Worst case we could support both.

Here is a plnkr example that I will make into a PR once we figure out which way we want to go with this.

[c0bra]

Seems like this change would also fix #2247. I'll look into it today.

[c0bra]

Problem is writing a test for this if we change it to setTimeout.

[c0bra]

OK I figured out a way to get the tests working. Let me know if I've broken everything.