Added DIRECTORY_SEPARATOR to workingDir

[darthvader666uk]

THis fix is further developed from this issue:

https://github.com/coenjacobs/mozart/issues/43

THis now appears to fix Mozart in Windows

[coenjacobs]

Hey @darthvader666uk, thanks for contributing this fix. To be honest, it doesn't sit well with me right now. This might be my bad, but I feel that the response of getcwd() can be something more than just the directory separator. In fact, for Unix based operating systems, just using the directory separator there (/) will result in Mozart using the root of the filesystem as the working directory. This will definitely lead to unwanted results.

I can imagine this being different on Windows though, where just the directory separator there (\) can be used to reference the current directory (if I recall correctly, after not having used Windows actively, for quite some time)? This might lead into a change that needs a separate bit of logic for just the Windows working directory selection. I need to properly test this in order to get it in a good enough state to merge.