add 165 to 721 (#972)

* 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

contracts/introspection/ERC165.sol

@@ -0,0 +1,20 @@
+pragma solidity ^0.4.23;
+
+
+/**
+ * @title ERC165
+ * @dev https://github.com/ethereum/EIPs/blob/master/EIPS/eip-165.md
+ */
+interface ERC165 {
+
+  /**
+   * @notice Query if a contract implements an interface
+   * @param _interfaceId The interface identifier, as specified in ERC-165
+   * @dev Interface identification is specified in ERC-165. This function
+   * @dev  uses less than 30,000 gas.
+   */
+  function supportsInterface(bytes4 _interfaceId)
+    external
+    view
+    returns (bool);
+}