Proposal for resolving clippy warnings

[Dalot]

I've decided to start to resolve this first on the present project so you can see if you like it.

It seems that in redisless case there wasn't much really important, it's mostly suggestions for idiomatic rust

~I am not sure why clippy complains about imports on src/cluster/tests.rs file, if there is some sort of a bug or anything I am missing in the compilation process. For now I have just included the ifcfg crate.~ Well, I shouldn't work that late, it was just missing the #[cfg(test)] annotation on the module.

A few #[allow(dead_code)] here and there since the repo is WIP...

[tbmreza]

I'm happy to see someone else has started working on those warnings 😄 I believe the next logical step is to prevent such lint errors to pile up again, maybe include running clippy in the CI tests? @evoxmusic