Avoid jQuery's .find in live loop

When .find is invoked in the live loop, it screws up Chrome's style
inspector.

Thanks, Andrew Dupont!
https://github.com/uploadcare/uploadcare-widget/blob/no-when-ready/app/assets/javascripts/uploadcare/core/jquery.1.7.2.js#L5143
Merge with master
Merge pull request #59 from uploadcare/live-fix

Live fix (stop flickering in Chrome's style inspector)