* Transaction API
* Merkle tree API
    * src/old/spend.rs for merkle_hash() function
    * Look at zcash_primitives::merkle_tree::CommitmentTree class
* Higher level language:
    * Lisp / Racket
    * PyPEG
    * lark-parser has a Python3 grammar
    * Pyparsing
    * tokenize
* Finish mint and spend contracts in new ZK language
* Save/load setup parameters using zcash API
    * How big are the params?
    * See zec.rs
* Command line tool to use VM
    * Take params in as a json
* Poseidon hash
* PoS spec