[CHEF-4024] Allow chef-solo to strip leading paths from recipes tarball

http://tickets.opscode.com/browse/CHEF-4024

When using chef-solo with tarball recipes, the only thing that prevents chef-solo from downloading the tarball directly from github is the fact that github's tarball adds some leading paths into it.

With this patch it's possible to strip leading paths using tar's strip-components options to remove those leadings path, making chef-solo a more flexible tool.