* make _tokenId indexed in Transfer and Approval events
via: https://github.com/ethereum/EIPs/pull/1124/files
* fix: make name() and symbol() external instead of public
* feat: implement ERC721's ERC165
* feat: erc165 tests
* fix: don't use chai-as-promised in direct await
* fix: reorganize to /introspection
* feat: abstract all erc165 tests to a behavior
* feat: disallow registering 0xffffffff
