Implement ETH Hash Verification

### Title

      OIP: 1004
      Title: Implement ETH Hash Verification
      Author: Mason Fischer <mason@kissr.co>
      Status: Draft
      Type: Standard
      Layer: Consensus
      Created: 2018-04-04

### Abstract

We need to implement ETH hash verification so we can validate blocks in the Ethereum Blockchain.

### Specification

https://github.com/ethereum/wiki/wiki/Ethash

