Setup on windows

Updated to allow setup on a windows box.
It's very unfortunate that we have to hardcode the full path like this. If user has a different version of mongo it would be a false negative. I don't have a better suggestion as mongo does not create any environment variable and it's not in the `PATH`. :(

Although because we don't start mongo in this script, and we check connection later, I see little value in having this check here. If instead we just skip this for win32, we'll fail later when trying to connect and we can advise the user to install and have mongo running before calling install again.