Use absolute paths instead of relative

Problem: The new version (0.16.0) of `CocoaPods/Xcodeproj` gem broke the
generation of ib.xcodeproj so that my XCode thought that resources were
in `/Users/username/code/project/resources/resources` path.

Solution: Using `Dir.pwd` and prefixing all the paths fixed it.
Merge pull request #58 from imalijkh/im-relative-paths-to-absolute

Use absolute paths instead of relative