include all provided args, even if false
insert the new content in the middle of the file, after the initial preamble, instead of right at the front

For this to work on [ModuleBuildTiny], we need a new release for
Leont/dist-zilla-plugin-modulebuildtiny #8
(https://github.com/Leont/dist-zilla-plugin-modulebuildtiny/pull/8)