Jennis/add gi.repository to ignored pylint modules

gi.repository module is now ignored by pylint

Because this module dynamically adds classes, false warnings such as "no-name-in-module" or "no-member" are outputted by pylint.

pylint and pep8 now run by default

Linting tests are now run by default when executing: ./setup.py test on the command line.

PLEASE NOTE: The additional CI job for linting has been removed.

From @tristanvb: "It is more important that developers find errors quickly and avoid wasting time pushing untested branches to CI, than it is nice to have a separate test in CI to view linting errors - if we can have both, we can re-enable that later without changing the default for the developer running tests locally."