Bug from removing USE_PERSISTENT

...101b89a00b0f21d5b28f67

The use of USE_PERSISTENT was needed as it was because of the behavior of require statements within rescue blocks

Alternatively, we could revert https://github.com/carlhuda/bundler/commit/ec49087a5acef97cf4101b89a00b0f21d5b28f67

Here's a gist illustrating the issue: https://gist.github.com/dmueller/5164088

I'm open for advice on where/how to write tests to verify the minor change in my pull request.