Support for new ERC721 interface

- Tests for new features are pending
- ERC721 is abstract, since it requires metadata implementation
- Move some methods into DeprecatedERC721 contract
- Reorganise base vs full implementation
- Pending tokenByIndex

contracts/AddressUtils.sol

@@ -0,0 +1,11 @@
+pragma solidity ^0.4.18;
+
+library AddressUtils {
+
+  function isContract(address addr) internal view returns (bool) {
+    uint size;
+    assembly { size := extcodesize(addr) }
+    return size > 0;
+  }
+
+}

contracts/mocks/ERC721BasicTokenMock.sol

@@ -0,0 +1,17 @@
+pragma solidity ^0.4.18;
+
+import "../token/ERC721/ERC721BasicToken.sol";
+
+/**
+ * @title ERC721BasicTokenMock
+ * This mock just provides a public mint and burn functions for testing purposes
+ */
+contract ERC721BasicTokenMock is ERC721BasicToken {
+  function mint(address _to, uint256 _tokenId) public {
+    super.doMint(_to, _tokenId);
+  }
+
+  function burn(uint256 _tokenId) public {
+    super.doBurn(_tokenId);
+  }
+}

contracts/mocks/ERC721TokenMock.sol

@@ -1,16 +1,35 @@
 pragma solidity ^0.4.18;
 
-import "./BaseERC721TokenMock.sol";
+import "./ERC721BasicTokenMock.sol";
 import "../token/ERC721/ERC721Token.sol";
 
 /**
  * @title ERC721TokenMock
- * This mock just provides a public mint and burn functions for testing purposes.
+ * This mock just provides a public mint and burn functions for testing purposes,
+ * and a mock metadata URI implementation
  */
-contract ERC721TokenMock is ERC721Token, BaseERC721TokenMock {
+contract ERC721TokenMock is ERC721Token, ERC721BasicTokenMock {
   function ERC721TokenMock(string name, string symbol)
-  BaseERC721TokenMock()
+  ERC721BasicTokenMock()
   ERC721Token(name, symbol)
   public
   { }
+
+  // Mock implementation for testing.
+  // Do not use this code in production!
+  function tokenURI(uint256 _tokenId) public view returns (string) {
+    require(exists(_tokenId));
+
+    bytes memory uri = new bytes(78);
+
+    uint256 i;
+    uint256 value = _tokenId;
+
+    for (i = 0; i < 78; i++) {
+      uri[7 + 78 - i] = byte(value % 10 + 48);
+      value = value / 10;
+    }
+
+    return string(uri);
+  }
 }

contracts/token/ERC721/DeprecatedERC721.sol

@@ -0,0 +1,10 @@
+pragma solidity ^0.4.18;
+
+import "./ERC721.sol";
+
+contract DeprecatedERC721 is ERC721 {
+  function takeOwnership(uint256 _tokenId) public;
+  function transfer(address _to, uint256 _tokenId) public;
+  function tokensOf(address _owner) public view returns (uint256[]);
+}
+

contracts/token/ERC721/DeprecatedERC721Token.sol

@@ -0,0 +1,35 @@
+pragma solidity ^0.4.18;
+
+import "./DeprecatedERC721.sol";
+import "./ERC721Token.sol";
+
+contract DeprecatedERC721Token is DeprecatedERC721, ERC721Token {
+  /**
+  * @dev Claims the ownership of a given token ID
+  * @param _tokenId uint256 ID of the token being claimed by the msg.sender
+  */
+  function takeOwnership(uint256 _tokenId) canTransfer(_tokenId) public {
+    require(msg.sender != ownerOf(_tokenId));
+    clearApprovalAndTransfer(ownerOf(_tokenId), msg.sender, _tokenId, "", false);
+  }
+
+  /**
+  * @dev Transfers the ownership of a given token ID to another address
+  * @param _to address to receive the ownership of the given token ID
+  * @param _tokenId uint256 ID of the token to be transferred
+  */
+  function transfer(address _to, uint256 _tokenId) public {
+    address owner = ownerOf(_tokenId);
+    require(owner == msg.sender);
+    clearApprovalAndTransfer(owner, _to, _tokenId, "", false);
+  }
+
+  /**
+  * @dev Gets the list of tokens owned by a given address
+  * @param _owner address to query the tokens of
+  * @return uint256[] representing the list of tokens owned by the passed address
+  */
+  function tokensOf(address _owner) public view returns (uint256[]) {
+    return ownedTokens[_owner];
+  }
+}