[#862]: Replace slashes for path with DIRECTORY_SEPARATOR

I suspect that the issue mentioned in #682 comes from the routing. The routing
uses '/' instead of directory separator and it would seem that this is not
translated to the OS' specific separator.

By replacing the '/' with DIRECTORY_SEPARATOR I hope it will solve the issue.
Merge pull request #877 from mvriel/862

WIP: [#862]: Replace slashes for path with DIRECTORY_SEPARATOR