Use Neil Fraser's diff instead of John Resig's.

John Resig's algorithm does weird things with block moves, and is
word-based which can cause some issues with long "word-like" strings.

Neil Fraser's algorithm gives better semantic output.

John Resig's diff: http://ejohn.org/projects/javascript-diff-algorithm/
Neil Fraser's diff: http://code.google.com/p/google-diff-match-patch/