Trinity support (with Juno)

[lrettig]

requires #35

https://notes.ethereum.org/qLkb-NM_R2eDgVGAy8n6WQ?both
ethereum/py-evm#923
https://github.com/lrettig/juno

[lrettig]

@poemm and I began working on this. I've got a barebones PoC passing a single ewasm state test in py-evm. See MD doc linked in description for our current proposals about how to carry out the integration.