Implement a stat interface

[scriptjs]

Random access classes lack a generalized stat interface to obtain basic information about the store such as its size. In both file and memory implementations, a length property is available to be used in such an implementation. That said, an optional stat property should exist in the abstract for implementors to establish methods that conform to this API, so consumers can examine stats for their stores.

[juliangruber]

Would it be possible for you to support this issue with some code or a specific use case?

[scriptjs]

@juliangruber I have been chatting with @mafintosh who has indicated he is taking the lead to rewrite the abstract random class. As a result, I must wait to see the next iteration of this class before proceeding. As far as the use case, my own is to help determine resource utilization for storages and archivers implementing random abstract.