new() doesn't work on artifact

In Truffle, I can create new contract instance by calling new() function on artifacts, but it seems not working with Tronbox. See [my repo](https://github.com/fyang1024/tronbox-testbed.git)
<img width="650" alt="screen shot 2018-12-04 at 12 39 30 am" src="https://user-images.githubusercontent.com/20808865/49377013-191ab500-f75d-11e8-84fe-c95d4de06c91.png">
