Bugfix/issue 289

Not sure if we want to do this, but it does fix the issue on iOS 7.

If you're doing a LOT of heavy lifting in your `table_data` (hint: you should spin off a thread and update the hash when you're done), then this will affect performance.

I think we can safely merge it. What say you, @markrickert and @silasj ?

cc @GantMan