Support environmental prefix

[Yadvendar Champawat]

Problem: Current version of the package does not support environmental prefixes, hence if a common redis instance is being used between two environments (lets say alpha and beta) then there is no mechanism to ensure that consumers/workers are executing jobs from producers of that particular environment or some other.
Proposed solution: One of the approach is to prefix the environment string to all the redis keys. Hence, there should be a feature to set prefix which varies as per the environment. Also, before implementing that at go layer, the hard coding of keys in the lua script should also be configurable in the sense that it should accept prefix as one of the arguments.