vero: add .alias()

cc @calvinfo 
closes #59 

users:
![screen shot 2014-03-25 at 8 22 33 pm](https://f.cloud.github.com/assets/1661587/2516132/bd88cd08-b44a-11e3-9e83-cc0e8524d11b.png)

logs:
```bash
identify "8baj5ju"
alias    "8baj5ju" -> "qi5h6fb"
```