Support for Solidity 0.8.x

[kclowes]

What was wrong?

Solidity 0.8 just came out, and we should check to see what we need to update. The Release blog post can be found here.

How can it be fixed?

This will likely be an issue that needs to be broken up into a few issues, but for starters, go through the changelog and write some tests for changes. On first glance, here are a few items that we'll probably need to handle:

• updates to revert - new error codes and a new Panic. EDIT: See comment here
• Make sure we support ABI encoder v2