Update pylint to 1.3.1

This is just to keep us on the upgrade treadmill. ([Changelog](https://bitbucket.org/logilab/pylint/src/9dce395369d32587f2c72c9f128523cfabbd1548/ChangeLog))
I don't know. I doubt it -- 12 is the default value from ``pylint --generate-rcfile``