Implemented LOG. Closes #159

tests/helper/vm.go

@@ -50,6 +50,7 @@ func (self *Env) Difficulty() *big.Int   { return self.difficulty }
 func (self *Env) BlockHash() []byte      { return nil }
 func (self *Env) State() *ethstate.State { return self.state }
 func (self *Env) GasLimit() *big.Int     { return self.gasLimit }
+func (self *Env) AddLog(vm.Log)          {}
 func (self *Env) Transfer(from, to vm.Account, amount *big.Int) error {
 	return vm.Transfer(from, to, amount)
 }