Add Callable in method get / set to handle if catch miss.

[smling]

As developer,

I need to make a convenient way to assign value when cache missing when get / set in redis.

So that I don't need to handle cache missing when get and need to set it to redis again.

PoC repository: https://github.com/smling/redis-extension

[sazzad16]

@smling Thank you for your interest in Jedis and willingness to improve it.

This idea does not align with the near future plans for Jedis. But let's see if this idea makes other users interested as well.