Doesn't return nodes with no children when looking for records to return

I was having an issue (left an issue in your issues list) where when i queried for something that returned zero records - i was getting an object with all the properties null.

Working this out, I got the GetNamedNodes method.   I noticed that MS recommended to use the SelectNodes method. 
http://msdn.microsoft.com/en-us/library/xzbctxhh(v=vs.110).aspx

This also seemed to be the best way to specify that we only wanted nodes with children.
I tested this with my basic implementation and it seemed to work ok.  Since its a fairly base method, i'm not sure if there are things using it and expecting there to be just the node with no children.  (which this change would break).   If it does break somthing - maybe this could be an overload for the calls that really don't want elements without children (ReadArrayResponse ) 

I was going to add a unit test or two, but it seems like we would need some sort of shared zuora api account to do this.