Cannot parse block_info transactions into SignedTransaction objects

[grzracz]

Subject of the issue

SignedTransaction.undictify does not work on block_info transactions from block_info().block.txns

Steps to reproduce

1. Fetch block_info using Algod client
2. Try to parse transaction for transactions using SignedTransaction.undictify

Expected behaviour

Transactions get parsed into objects. Potential solution could be to have an additional method that parses the entire block into readable data.

Actual behaviour

Bunch of errors where undictify assumed keys are bytes and not base64 encoded strings

[grzracz]

In order to make this any useful Transaction object would also need to include state deltas

[jannotti]

#531 is working on this.

Rather than changing Transaction, it adds SignedTxnWithAD which is the name of the structure that contains the Transaction, signature, and ApplyData in the Go code.