Tidy up

[Edd]

• Remove old_contracts
• Verify that any notes.txt esque files are either deleted or merged in to a readme.md`
• Ensure that instructions are up to date (one mentions kill-contract.js which doesn't exist)`

[Danny (Sacrificial Pancakes)]

All of the updates are on the (internal_contract_audit) branch along with all the other changes woo.