Add code to handle config files specified with the --prepend-config
argument.
Options specified in prepend files get a higher precedence than flake8
defaults but a lower one than user configs. This allows to override
the defaults without affecting the behaviour of user and local config
files.
This implements a solution for issue #349
Previously Flake8 parsed both
max-line-length = 110
And
max_line_length = 110
From the config file without issue. When we updated our logic, I forgot
to test for that and we lost that behaviour temporarily.
Closes#152
This relies on two things:
1. Properly configuring flake8-import-order to use that style
2. Properly configuring flake8-import-order to know that flake8 is our
application name.
