5953 dodge npm link error

@walpurgisriot @fishyfriend @jake-miles 

This PR fixes a problem with sharing contract objects between 2 instances of the library, which can occur when using `npm link`.
Javascript types carry their type as the return value of typeof.  For example, 
```
var contractType = typeof (new Contract ("0", value(0)));
var isTypeContract = function (x) { return typeof(x) === contractType }
```