Fix Safari 6 toString() bug

Merged from https://github.com/jaywilliams/SlickGrid/commit/6b8de2183491408e1d89ed7c7981c24d9f276dc2.
Applied fix to destroy error with JQuery 1.9.
Merge pull request #597 from beckstea/JQuery-1.9-Fix

Applied fix to destroy error with JQuery 1.9.
Merge remote-tracking branch 'remotes/mleibman/master' into rowspan