Close #458 by proving that there is no failure

This pull request closes issue #458 by implementing a test that shows that it is possible to stub fs.readFileSync. I've run the tests on node 0.10.25 and 0.10.29 and cannot reproduce the bug.
Merge pull request #528 from mroderick/issue-458-stub-readFileSync

Close #458 by proving that there is no failure