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.

Previously, pycodestyle never introspected the argument names for
classes except to require that ``tree`` be an argument it could pass.
For Flake8 3.0, we lifted that restriction, but old plugins seem to
have cargo-culted their __init__ signature to be

    def __init__(self, tree, builtins=None):

For some yet unknown reason. This was causing an AttributeError. By
updating flake8.utils.parameters_for to return a dictionary that
indicates whether the parameter is required or not, we can side-step
this by simply ignoring the parameter if it has a default value and
we cannot provide it.

Closes #151

This fixes a regression in behaviour from 2.x to 3.

Closes #150

This is an emerging best practice and there is little reason to not
follow it