Design and implement proper Redis module API validation

[MeirShpilraien]

Different Redis version expose new API that is not presented on old versions.
We should define a solution that will allow the user understand which API he can and can not use and avoid mistakes either on compile time or on runtime.

[oshadmi]

For compile time would require to define a min redis version?

[iddm]

We can use features to specify the Redis version, and in the code use cfg_if! and #[cfg] to enable/disable the code paths relevant.

[MeirShpilraien]

Draft proposal: #304