Made sure newlines are removed from the system paths

When trying out the `application_finder` branch, I got:

    OSError: [Errno 2] No such file or directory: '/usr/games\n'

So I've fixed the `system_path` method in `master`, which removes the bug. I wasn't sure if `.replace('\\n','')` was also needed, so I left it in.

I'll suspend the pull request for the `application_finder` branch until I've had a good look at the whole thing, to make sure there aren't any other small bugs.