Previously, to ensure that plugins on by default were reported, we
added them to the select list. This means that ignoring them became
impossible. To accomodate our reporting logic and a user's ability
to ignore, we need to keep our select and extended select lists
separated.
This allows us to have a better understanding of who is selecting what,
where, and how and make our decision as to whether or not an error
should be reported more wisely.
Closes#195
This makes the regular expression a bit more complex, and potentially
slower, but it will fix the issue where users had noqa comments with
colons followed by explanations.
Closes#178
