Part of #7.
This MR has fixed the remaining clippy::style lints.
The interesting commits are:
write_list!, started in !42 (merged)
String::push_str (with the corresponding push_str_list! macro) instead of write!, which require disabling a clippy lint [1], considering the following interesting comments [2].[1] See https://rust-lang.github.io/rust-clippy/master/index.html#/format_push_string: write! require doing an unwrap that cannot fail. However, String::push_str with a format! would require an unnecessary heap allocation, resulting in the clippy lint mentioned.
[2] See comments of https://github.com/rust-lang/rust-clippy/issues/9077