1. Stringify $hash request arg at Net::Ethereum methods:
   - eth_getTransactionByHash
   - eth_getBlockTransactionCountByHash
   - eth_getTransactionReceipt
   - retrieve_contract
2. Remove %*ENV<SCHASH> from tests
3. Get smart contract addr from tx hash (%*ENV<TXHASH>, @*ARGS[0])
4. Refactor tests and add some hash-check tests to
   - ./t02.t
   - ./t04.t
   - ./t05.t