Implement Send & Sync for EnumSet<T> #78
Description
I think it would be cool if EnumSet<T> was Send and Sync for a generic T and I don't see a reason as to why it couldn't be. As I've understood it EnumSetType::Repr will always in practice be a primitive (or array thereof). Therefore, adding Send and Sync as supertraits of EnumSetTypeRepr should not be a breaking change whilst making EnumSet<T> thread safe.
I can make a PR.