-----------------
* Implement GET/PUT objects by natural_key and minor fixes.
* General
+ Upgraded ``drf-nested-routers==0.11.1``
+ Re-organized nsot.api.urls to improve readability
+ Implemented natural_key mappings for Device and Network resources
* Networks
+ Updated ``Network.objects.get_by_address()`` to support optional site=
argument for filtering by site_id.
* Serializers
+ Moved ``.create()``, ``.update()`` methods from Device, Network serializers
to new ``ResourceSerializer`` base.
* Change Events
+ Fix when deleting a resource object using the API failed for any
reason the "Delete" change event would still be created. The Change
event will now only be kept *after* a successful delete.
* Views
+ Implemented ``NsotViewSet.get_object()`` support for nested serializers
+ Updated Network lookup_value_regex to support loookup by pk or
IPv4/IPv6 natural_key.