SimpleChaincode example simple Chaincode implementation
type SimpleChaincode struct{}
func (t *SimpleChaincode) Init(stub shim.ChaincodeStubInterface) pb.Response
Init takes two arguments, a string and int. These are stored in the key/value pair in the state
func (t *SimpleChaincode) Invoke(stub shim.ChaincodeStubInterface) pb.Response
Invoke is called by fabric to execute a transaction