Looks like this package depends on a custom fork of CSSLint (https://www.npmjs.com/package/atomlinter-csslint / https://github.com/AtomLinter/csslint).
This does not allow for getting newer versions of CSSLint coming from https://github.com/CSSLint/csslint
I contributed to core project - documentation URLs to all the rules and looked to surface them in Atom linter so developers can click right from message bubbles and open detailed documentation in the browser .