Improve pylint source handling

pylint does not need the source tree, so do not use inplace files
anymore.  Allows pylint to check the module name, too, since it's not
longer changed by Flycheck.
[Fix #204] Do not ignore Pylint convention messages
Merge branch 'feature/pylint-convention-warnings'

* feature/pylint-convention-warnings:
  [Fix #204] Do not ignore Pylint convention messages
  Improve pylint source handling