cargo clippy warns on unused lifetime

[lumag]

I'm getting the following warning when used with cargo clippy:

warning: this lifetime isn't used in the impl
--> src/options.rs:6:39
|
6 | #[derive(Clone, PartialEq, Eq, Debug, EnumKind)]
| ^^^^^^^^
|
= note: #[warn(clippy::extra_unused_lifetimes)] on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_lifetimes
= note: this warning originates in the derive macro EnumKind (in Nightly builds, run with -Z macro-backtrace for more info)