Icons corrupt on zoom?

[Alex-Ikanow]

Hey apologies if this is already fixed (I'm running an older version, which I've modified and don't have time to merge just now) - it did happen on the examples (eg) on dev.datasift.com for what that's worth, and I couldn't immediately see it in the closed issues list.

This is very simple to reproduce: bring up the datasift editor in chrome, and zoom in: all the icons become "corrupt", examples:

Big fan of the query editor, incidentally, nice work!