Nsot

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* Complete overhaul of API filtering to use DRF built-in filtering.
* All overloads in views of .get_queryset() has been removed and
replaced with ``filter_class`` objects stored in ``nsot.api.filters``
* All Resource filtering is now done using built-in
``DjangoFilterBackend`` objects using either ``filter_class`` or
``filter_fields``.

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* Fixes 118 - Network objects are now round-trippable in API.

+ You may now provide either ``cidr`` or ``network_address`` +
``prefix_length`` when creating a Network object.
+ A Network object returned by the API may now be full used for create
or update, making them round-trippable.

* Verbose names and help text have been added to all Network fields, so
that they display all pretty like.

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* Added X-Forward-For into request logging.
* Also added an API test for sending X-Forward-For

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* Full support for PATCH in the API and some resultant bug fixes to PUT.

+ Specifically, this means any resource that is allowed to have
attributes can now be partially updated using PATCH, because PATCH
operations have been made attribute-aware.
+ Attributes themselves cannot YET be partially updated, but we hope to
address that in a future... PATCH.

* Serializers

+ PATCH support enabled for complex objects: Attributes, Devices,
Interfaces, Networks.
+ ResourceSerializer subclasses now all inherit default behavior for
handling attributes. The ``.create()`` and ``.update()`` methods now take
an optional ``commit=`` argument to toggle whether to save an object after
updating attributes. This is so that descendent serializers subclasses
can overload this method and not call save until they choose (such as
in Interface serializers).
+ Each resource now has PUT and PATCH serializers broken out explicitly
to facilitate the "optional fields" nature of PATCH vs. the "mandatory
fields" nature of PUT.

* Attributes

+ All error messages raised when validating attributes include the word
"attributes" so that you know it's a validation error specific to
attributes.

* Bug Fixes

+ Bugfix in handling PUT requests where attributes would be initialized
if not provided. Attributes are now mandatory on any PUT requests and
will result in an error if they are missing.
+ Bugfix when assigning more than one IP address from the same network
to an
Interface that would result in a 500 error (and unit tests now catch
this).

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* Bugfixes w/ natural_key lookups that would result in a 500 error.

+ Turns out that ``site_pk`` was incorrectly being dropped when doing
natural_key lookups, which would result in a 500 w/ multiple
sites.
+ We now detect when multiple objects are returned when looking up
resources by natural_key and display a helpful 400 error.
+ Reverted top-level URL router back to Bulk default router because the
SimpleRouter base doesn't provide api-root, and we kind of (really)
want that.

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* Issue 50 - Adds better device name validation
* Fixed regex to match DNS hostname requirements. Added unit tests for device name checking
* Fix device name / attribute name comment