ERC721Deed

[nastassiasachs]

Fixes #627 Implement ERC standard

🚀 Description

Recently deed has been introduced as a term to refer to non-fungible tokens (see ethereum/EIPs#841). This is an attempt at implementing the current state of the ERC721 interface.
(Sorry, I don't know why the Bounty contract tests failed on my end.)

• [ x ] 📘 I've reviewed the OpenZeppelin Contributor Guidelines
• [ x ] ✅ I've added tests where applicable to test my new functionality.
• [ x ] 📖 I've made sure that my contracts are well-documented.
• [ x ] 🎨 I've run the JS/Solidity linters and fixed any issues (npm run lint:all:fix).

[spalladino]

Thanks for the PR @nastassiasachs, but we understand there was no consensus around the rename to deed. I'm closing this issue now, and the full implementation for ERC721 is continuing in #803.