Allow config args to be not first

[benjamin-fenker]

Resolves #265

[tbooth]

I see what this PR is getting at but I feel like it might not work in all cases. I think we definitely need some extra tests before accepting this change.

Also, some nitpicks:

• Avoid using a list comprehension for side effects. The first one is fine, but the second should be an actual for loop
• The comments in the code should be changed in line with the code changes