Get children taxons ordered 

Hi,  I like and use  this bundle but I've found an couple of problems about the Taxon entity mapping
-If we don`t set order-by attribute in children relation, we get children ordered by id not by left.
-The right order is "left ASC".

According with https://github.com/l3pp4rd/DoctrineExtensions/blob/master/doc/tree.md#xml-mapping-example.

Thanks for your time!