Removed rustfmt_skip guards from all files.

[Zenithsiz]

This PR removes all #![cfg_attr(rustfmt, rustfmt_skip)] from files so that files are automatically formatted by IDEs and using cargo fmt when working on this crate.
It might also be worth considering adding a github CI action to make sure the crate is fully formatted, this can be done with cargo fmt --verbose -- --check.

The reason for this PR is to make it easier for people to contribute without worrying about formatting. Recently I created a local branch to make a PR, but since I use hard tabs, I had to reformat my code manually every few lines, which became annoying quickly.
I believe it is standard for rust projects to use rustfmt to format their code. This can also be customized with a rustfmt.toml file if you wish to enforce a specific format.
It is also possible to put a #[rustfmt::skip] attribute on functions / blocks that shouldn't be formatted for some reason (such as the full ascii table in AsciiChar::new) to manually avoid this.

[tomprogrammer]

I fully agree that the code should be formatted by default. I'll add an editorconfig file, editors that understand the file will use spaces for this project even if rustfmt is not used.