Remove ‘+’ from the end of a kernel version string

CoreOS does this to indicate that the kernel sources differ from the
official tree.
Merge pull request #16 from ace-cookbooks/fix-forked-kernel

Remove ‘+’ from the end of a kernel version string
Fix for network detection on non-linux OSes
Guarantee the tarball output directory
Merge pull request #17 from ace-cookbooks/consistent-tar

Guarantee the tarball output directory