https://rust-lang-nursery.github.io/edition-guide/print.html#no-more-extern-crate https://rust-lang-nursery.github.io/edition-guide/rust-2018/macros/macro-changes.html https://github.com/iceiix/steven/pull/13#issuecomment-435702507
Resolves most of https://github.com/iceiix/steven/issues/1