Merge remote-tracking branch 'upstream/master' into elopio-refactor/1…

…175/event-underscores

contracts/token/ERC721/ERC721Basic.sol

@@ -60,21 +60,18 @@ contract ERC721Basic is SupportsInterfaceWithLookup, IERC721Basic {
     return owner;
   }
 
-  event Transfer(
-    address indexed from,
-    address indexed to,
-    uint256 indexed tokenId
-  );
-  event Approval(
-    address indexed owner,
-    address indexed approved,
-    uint256 indexed tokenId
-  );
-  event ApprovalForAll(
-    address indexed owner,
-    address indexed operator,
-    bool approved
-  );
+  /**
+   * @dev Approves another address to transfer the given token ID
+   * The zero address indicates there is no approved address.
+   * There can only be one approved address per token at a given time.
+   * Can only be called by the token owner or an approved operator.
+   * @param _to address to be approved for the given token ID
+   * @param _tokenId uint256 ID of the token to be approved
+   */
+  function approve(address _to, uint256 _tokenId) public {
+    address owner = ownerOf(_tokenId);
+    require(_to != owner);
+    require(msg.sender == owner || isApprovedForAll(owner, msg.sender));
 
     tokenApprovals[_tokenId] = _to;
     emit Approval(owner, _to, _tokenId);

contracts/token/ERC721/IERC721Basic.sol

@@ -40,19 +40,19 @@ contract IERC721Basic is IERC165 {
    */
 
   event Transfer(
-    address indexed _from,
-    address indexed _to,
-    uint256 indexed _tokenId
+    address indexed from,
+    address indexed to,
+    uint256 indexed tokenId
   );
   event Approval(
-    address indexed _owner,
-    address indexed _approved,
-    uint256 indexed _tokenId
+    address indexed owner,
+    address indexed approved,
+    uint256 indexed tokenId
   );
   event ApprovalForAll(
-    address indexed _owner,
-    address indexed _operator,
-    bool _approved
+    address indexed owner,
+    address indexed operator,
+    bool approved
   );
 
   function balanceOf(address _owner) public view returns (uint256 _balance);