This adds support for rules that ignore violation codes on a per-file
basis. This takes a similar functional approach to
https://github.com/snoack/flake8-per-file-ignores which allows for glob
patterns like the `--exclude` option.

Closes #156

Instead of just using Flake8 and pylint to keep Flake8 clean, let's also
use black to make it less manual for clean-up.

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

By ordering the plugins, --version becomes reproducible so that it
continuously prints the same output (provided the plugins have not
changed).

Closes #297

When invoked it will print out JSON that has all of the debugging
information needed by the maintainers to diagnose or reproduce a bug.

Closes #207

Previously, all testing was done from the directory in which the
configuration file lived, so this bug went unnoticed. However, if you
run Flake8 against its own source from a directory above, you would
notice that the patterns in the exclude config value in tox.ini were
ignored. This is because we (like any reasonable person) are using
relative paths. The path is relative, however, to the directory in
which the configuration file was located. So we keep track of which
directory that is and use that to normalize the paths in the config
file.

Yes, there is an unrelated change to our tox.ini in this commit as
well. ;-)

Closes #194

If a user specified `--max-complexity` on the command-line, they
would be told that it did not exist. The same would be true of any
option provided by a plugin. This is because we parse the command-line
arguments twice in Flake8 -- the first time to specify the verbosity
and destination for logging, the second time to actually execute Flake8.
Since plugin options are not registered to start with the first time,
they are not valid options. So when we first parse the options, we should
only attempt to parse the ones which we know about.

Closes #168

When flake8's config is in setup.cfg, setuptools attempts to set those
options on the command instance. If they don't exist, it fails early
complaining that a specific option does not exist.

This adds this back and does it better than the Flake8 2.x version.

Closes #163

On Flake8 2.x we added the information about the implementation,
version, and operating system to the --version output to make helping
users easier. In short they can pretty simply just give us the output
from

    flake8 --version

And we can get a lot of the information that we need.