Drive letters on Windows should not be case-sensitive

[sgarcialaguna]

This took me a couple hours to figure out.

Wanted to include grunt-qunit-istanbul in a Jenkins project - the test ran fine, but the coverage report was empty. Running 'grunt qunit' manually worked fine. Eventually I found that Jenkins used 'd:\Jenkins' as a workspace path and I used that path in my call to grunt. Changing it to 'D:\Jenkins' fixed the issue.