Package name and a quirk with dash (hyphens)
Rust supports underscores (_) for package names but not hyphens (-). However, you may see packages on Crates.io with hyphens.
The related RFC recommends explicitly renaming those crates with underscores. E.g.
extern crate "rustc-serialize" as rustc_serialize;
There is quite a bit of debate about whether hyphens should be used in library names.
Refraining from using hyphens seems to be the most future-proof option, but I agree with the aesthetics aspect of using dash instead of underscore.