Path issues on case insensitive file systems

In exercism/exercism.io#3820 we discovered that when beeing in `~/exercism/javascript/hello-world` canceled submission because of not beeing in the workspace, as the configured workspace was `~/Exercism` (capital `E`!). Downloading exercises worked and files were accessible at the aforementioned uncapitalized path.

It seems as if we need to normalize pathes on mac as well similar how it is planned or already done for windows.