Bug with the whitespace and other delimiters in config

[vergeev]

It doesn't look like the config parser accounts for the case

directories_to_skip=build, dist, test_fixtures, .pytest_cache

because it doesn't strip whitespace:

'directories_to_skip': lambda x: x.split(',')

(see https://github.com/devmanorg/fiasko_bro/blob/master/fiasko_bro/configparser_helpers.py#L30)

I might also want to be able to do this:

directories_to_skip=
    build
    dist
    test_fixtures
   .pytest_cache

just like in any normal config.

Somebody has probably already written code for that.