RFObjectPool refactoring as mentioned in #43.

RFObjectPool refactoring as mentioned in #43.
NSDateFormatter local pool realizations are removed from coders/decoders in ROADSerialization and replaced with RFObjectPool.
I'm just saying it will be cool if pool can contain more than 1 object per `key`, so we can use few object per `key` at a time and then put them back. Right now it's not necessary so let leave it with that.