Add Windows compatibility to ImportPathForDir

[dissipative]

Fixes #786

[coveralls]

Coverage increased (+0.009%) to 61.686% when pulling 0d8167d on dissipative:fix-imports into d2c5bf2 on 99designs:master.

[vektah]

Sorry, we generally try to avoid if windows checks (except in tests).

I've fixed this in #822, instead of looking for / it stops as soon as the parent dir has the same path as the current dir.