Allow newer OSX versions to pass version check

DS script/bootstrap script failed when it run this script. as this script fails on passing the OSX version check for newer versions than 10.8 ML.

I've updated this to allow past any newer version than 10.8, an argument could be made that we should only specify versions we know this script runs successfully against, but that always (like currently) has the knock on effect of having to then update it when a new OS version is released (even if not very often)