Include linter class MD5 in linter version

Summary:
People constantly forget to bump the linter version and I don't see a way how to stop it.
This may bump the version even if it wouldn't be required but let's rather undercache than overcache.

Test Plan: `var_dump($version)`.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5129