Update documentation with new pyflakes error codes.

See merge request pycqa/flake8!300

- F632 and F633 were missing
- F721 and F722 were combined in the same row
- F723 was missing

Fix performance regression with per-file-ignores

Closes #501

See merge request pycqa/flake8!299

With a large number of errors, filenames, and per-file-ignores the style guide
selection would take a significant portion of execution time
(python3 70% / python2 99.9%).

Caching the styleguide lookup by filename eliminates this bottleneck.

Improve error message for malformed per-file-ignores

Closes #489

See merge request pycqa/flake8!298

Gracefully ignore flake8-per-file-ignores if installed

See merge request pycqa/flake8!297

Fix typo in 3.7.2.rst

See merge request pycqa/flake8!296

Fix flake8 --statistics

Closes #499

See merge request pycqa/flake8!295

Make uses of typing compatible with python 3.5.1 / 3.5.0

Closes #498

See merge request pycqa/flake8!294

Fix legacy api invocation of make_notifier

Closes #497

See merge request pycqa/flake8!293

Fix bug flake8 --diff

Closes #490

See merge request pycqa/flake8!292

Fix plugin exception reporting keyerror typo

See merge request pycqa/flake8!275

I guess that if you don't have something python2 compliant to say. might as well say nothing at all
Also fix linter errors

Allow capitalized filenames in per-file-ignores

Closes #488

See merge request pycqa/flake8!290

Remove remnants from previous PRs

See merge request pycqa/flake8!289

- warnings in configparser were silenced upstream (unless `-3` is passed)
- we no longer invoke tests from `python setup.py test`

Upgrade entrypoints and sync with setup.cfg

See merge request pycqa/flake8!288

Latest pycodestyle

See merge request pycqa/flake8!287

Also copy deps to setup.cfg

See merge request pycqa/flake8!286