enables WKT BOX2D to Google Rectangle object

* Enables parsing of [PostGIS 2D Boxes](http://postgis.net/docs/Box2D.html) to create [Google Maps Rectangle](https://developers.google.com/maps/documentation/javascript/examples/rectangle-simple) objects. 
* Enables the write method to convert the Rectangle back to a 2D Box
* Ensures the precense of the class variable 'delimited'. I kept getting an undefined value.
* Forces the casting of X and Y coordinates to string in the point extract method, for the concatenation 
```
return point.x + this.delimiter + point.y;
```

was being evaluated as a numeric sum, thus returning NaN.