Catch UnicodeDecodeError while parsing config files

See merge request pycqa/flake8!208

Local plugins updates

See merge request !207

By slightly modifying our utility function to parse comma separated
lists we can parse local plugins similar to other configuration options.

This allows us to report whether or not a plugin is local when users
provide `flake8 --bug-report` output.

Lint only *.py files with --diff option

Closes #362

See merge request !206

Fix finding of local config files.

See merge request !204

When using the `--diff` option flake8 only lints *.py files or files
defined by the `--filename` filter.

Fixes #362

Simplify application tests; remove unneeded mocking

See merge request !205

Add support for local (in-repo, non-setuptools) plugins.

Closes #357

See merge request !197

See also https://gitlab.com/pycqa/flake8/merge_requests/198

Tell user how to configure VCS hooks

See merge request !198

dd missing release notes for 3.5.0

See merge request !202

Update pyflakes range and include doc links

See merge request !201

Add new pycodestyle checks

Closes #361

See merge request !199

Prepare master branch for development of 3.5.0

See merge request !200

Closes #361

Also fills out the hg install hook docstring.

This would close GitLab issue #335.

Closes #357

Allow spaces in # noqa lists

Closes #356

See merge request !196

To match our new configuration file format and its allowance for spaces
in the list

Closes #356

Fix regression in --select behaviour in v3.4.0

Closes #354

See merge request !195

Previously we were hitting the catch-all return that decided the error
was selected. Instead, let's add specific logic since we now know how we
would hit that and we actually don't want it to be selected.

Closes #354