pylint: include symbolic message name in output

pylint is moving away from the numerical message IDs (e.g. W0611)
because they are cumbersome and not descriptive when you come across
them in in-source pylint directives (e.g. # pylint: disable=W0611).

Instead, symbolic names are recommended, and much easier for humans
to use (e.g. # pylint: disable=unused-import).
(See http://docs.pylint.org/faq.html#do-i-have-to-remember-all-these-numbers)

This patch modifies the message output to print both the ID and
symbolic name for the current line in vim.