Note to self: Looks like this is called ```zone_name``` because when we accept it from the user it is the name of the zone, but when we return this model to the user, it is the url to the ```zone``` resource. 

@icco I'm thinking something along the lines of creating a Fog::Google::ZonedResource that zoned resources can inherit from. In the c'tor, we can try to perform these checks. (This could be done via mixins as well, I haven't thought through the advantages of inheritance v/s mixins for this case).