Use path.sep instead of forward slash

[petar-iv]

Hi,

This is more of a cosmetic improvement.
Currently, if one executes node test\test.js the output would look like the following:

C:\git-repos\node-diveSync/diveSync.js
C:\git-repos\node-diveSync/node_modules/append/append.js
C:\git-repos\node-diveSync/test/test.js

The path separator used (after the directory passed to the function) is always a forward slash which results in mixing back- and forward slashes on Windows.
With this change the output would look like the following:

C:\git-repos\node-diveSync\diveSync.js
C:\git-repos\node-diveSync\node_modules\append\append.js
C:\git-repos\node-diveSync\test\test.js

Thanks for having a look at this PR.