To be honest I'm unsure if grouping similar module in their own subfolders is actually desired - As is it doesn't match the way module source file lookup looks for them (hence the path attribute).

I originally introduced that `str` folder together with `ascii.rs` when I understood the module system far less than today. The only other modules that do this are the modules in the `num` directory (also introduced by me :| ), but those at least have the excuse of being horrible repetitive and macro generated.

If grouping string related modules into their own directory is desirable, even if it doesn't mirror the way module hierarchy source file lookup works, then I'd have to make a separate commit for also moving a bunch of other modules anyway to be consistent. Maybe I should make an issue about this.