Change to make osutils work cross-platform.

Previously some paths were not handled correctly under Windows. It seems ntpath supports all the paths I can throw at it, and still work under both Linux and Windows.
Removing assert

As per https://github.com/rgalanakis/brennivin/pull/4#discussion_r16304013
Merge pull request #4 from ccpgames/master

Change to make osutils work cross-platform.