V1

[RRostami]

Reworked the CacheLayer files and made it an interface.
Added support for client-side hash sharding.
Added rediscluster configuration which supports both sharding and Redis cluster.
Moved internal contexts into a better place.
(Breaking Change: outward-facing TTL now requires a context as well)
Reworked internal configs (paving the way for more flexible input config on a later date)
Also added some config examples

[mmohamadi]

Hi. I think it would be much better to collect common properties of different cache types into a new type.
For example there could be a type called commonCacheProperties which is implemented as
type commonCacheProperties struct {
layerName string
amnesiaChance int
compressionEnabled bool
cacheTTL time.Duration
watcher ITimer
}

then the new type can be embedded in each cache type
for example
type tinyCache struct {
commonCacheProperties
base *sync.Map
}

so, the need to repeat all of them over and over again is eliminated.

[pedramteymoori]

Well done @RRostami . I opened two tiny discussions. There is also one good suggestion from @mmohamadi here which is considerable.
I also found one ambiguity in our readme regarding integrating Epimetheus which is better to be addressed explicitly.
This PR will be ready for merge after these modifications.