* Add python api that generates desciptor(s) from the aligned image(s)

* Remove asserts from face_recognition.py example/tutorial

* In batch_compute_face_descriptors_from_aligned_images, use for-in loop to simplify the code

Improvde the document on binding methods and the error message if the aligned image is not of size 150x150

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

* Replace boost::python with pybind11

* Replace add_python_module with pybind11_add_module

* Fix clang error on type-dependent expression

* Exposed jitter_image in Python and added an example

* Return Numpy array directly

* Require numpy during setup

* Added install of Numpy before builds

* Changed pip install for user only due to security issues.

* Removed malloc

* Made presence of Numpy during compile optional.

* Conflict

* Refactored get_face_chip/get_face_chips to use Numpy as well.

In particular, these new functions don't need to be inside the face
recognition class.  So I moved them out.  I also fixed many incorrect
copy/pasted comments and clarified parts of the example code.

* improvements to cnn face detection interface

* mmod rectangle object renaming. possibility to set batch size in multi image detection. Added check to make sure images are all the same size.

* Add cmake option to use external libjpeg on Mac OS

* Add adjust_threshold to python object detector

* Add cmake option to use external libjpeg on Mac OS

* Add adjust_threshold to python object detector

* Revert "Add cmake option to use external libjpeg on Mac OS"

This reverts commit 01f7fd13ea3f2b519312900333f9b68847fd1633.

* Update detector example to set adjust_threshold