Handle genesis receipt

### What went wrong?

The genesis receipt comes back funny:

```python
In [6]: receipt = next(explorer.get_account_transactions(ZERO_ADDRESS))

In [7]: receipt
Out[7]:

In [8]: receipt.sender
Out[8]: 'GENESIS'

In [9]:
```

### How can it be fixed?

Change sender to ZERO_ADDRESS
Look into what we can do about txn hash, if anything

Start by reproducing the receipt returned by explorer.get_account_transactions(ZERO_ADDRESS) and inspect the Receipt fields shown in the report. The change is done when the genesis receipt reports ZERO_ADDRESS as sender and the handling or limitation of its transaction hash is documented by the resulting behavior.

Written by the indexing model from the issue text.