interface since AVX availability is now detected automatically by cmake.

* Fixed reference count issue

* Fixed refcount issue in Python dlib.jitter_image and dlib.get_face_chips

* Consolidation of https://github.com/davisking/dlib/pull/1249

* Fixed build issue

* Fixed: Paths in a pytest file should be relative to dlib root

* Skip numpy return tests for Python 2.7 or if Numpy is not installed

* Enabled numpy returns tests on Python 2.7 using cPickle.dumps

available in python3.

Also just cleaned up a few minor details.

A little bit hacky, but should be fine. Supports both fhog
detectors and the "cached" simple_object_detector. Also, maintains
the upscale parameter for testing

directly on already loaded data rather than needing to use an XML file as
input.

failure in the makedocs script

in color instead of always converting to grayscale.