Fix Issue #42: Better document createPath()

After many backs and forths on #42, the final code change is simply to update the comments to better understand what createPath() does (not) do.

If a "path" ends in a non-slash, then the final component of the path is assumed to not be a part of that path.  So, `a/b/c` will create a path `a/b` and assume c is a file name.  On the other hand `a/b/c/` will create all 3 path components.