add relative paths
move relative path to utility function
Merge branch 'relative_path' of https://github.com/mrijken/bowerstatic into mrijken-relative_path

Did a bunch of tweaks: the most important one is to expose
module_relative_path under the bowerstatic namespace instead of
exposing bowerstatic.utility.
Conflicts:
	CHANGES.txt
Merge branch 'mrijken-relative_path'