Break the OS X install specifics to its own file script/setup.osx.
Missed the test from the md5sum hard fail. This fixes the hang on md5 check during setup.
Let the user know we have completed the setup process if we had to run script/setup.
setup.osx file mode a+x.
Add install support for apt (Debian) based systems. This includes Ubuntu.
Actually skip apt packages that are already installed.