Display storage dump with state before revert

[DanielSchiavini]

What I did

• Save the contract repr with the computation in case of an error
• Use this value to show the storage state when the computation errored
• This should fix storage dump is wrong after reversion #92

How I did it

• Investigated how py-evm handles the snapshots
  • However, the data gets completely deleted after revert. To save all the deleted data would be quite cumbersome
• Instead of saving the whole journal, it makes more sense to only save the data we need when we need it
• Therefore I only extract the repr(contract) before the revert, as this is the information used
• Alternatively we could extract more data at this point (e.g. storage.dump())
• The implementation is in the environment as this is specific to py-evm

How to verify it

• Test is included; Please advise on extra test/corner cases that I did not identify.

Description for the changelog

• Display the storage dump with the state before the computation was reverted

Cute Animal Picture

[charles-cooper]

let's roll back the changes to the CI for now