cpuset: a bare-bones parser for the linux cpuset format

See: http://man7.org/linux/man-pages/man7/cpuset.7.html#FORMATS

License: APACHE v2

This package is meant to be minimal and trivial to embed in projects. The API is very unlikely to be extended. For a more comprehensive package: https://github.com/kubernetes/kubernetes/tree/master/pkg/kubelet/cm/cpuset

Please contribute testcases and fixes!