concat not working in Windows?

[torjue]

Seems like the concat option isn't working in Windows, when used with usemin, due to path issues. Same gruntfile works on osx/linux.

[ericclemmons]

Thanks for the screenshot! I believe grunt.util has something I can use to detect the file system or figure out the usemin path.

I'll figure it out, but will probably need your help on it :)