* Align ERC721 Receiver with current ERC721 standard.
Adds a second address field to onERC721Received
onERC721Received(address,address,uint256,bytes)
Updates the function signature to 0x150b7a02 from 0xf0b9e5ba

* Add _operator to onERC721Received

* Fix error caused by formatOnSave

* Fixed comments on ERC721Receiver
Removed "Must use 50,000 gas or less"
Corrected the function signature