Merge branch 'docs' into 'master'

bob/learn/tensorflow/configs/style_transfer/vgg19_example.py

bob/learn/tensorflow/dataset/__init__.py

bob/learn/tensorflow/estimators/Logits.py

bob/learn/tensorflow/estimators/Siamese.py

bob/learn/tensorflow/estimators/Triplet.py

bob/learn/tensorflow/estimators/__init__.py

bob/learn/tensorflow/network/InceptionResnetV1.py

bob/learn/tensorflow/network/InceptionResnetV2.py

bob/learn/tensorflow/network/__init__.py

bob/learn/tensorflow/utils/util.py

doc/conf.py

doc/img/angelina.jpg

doc/img/angelina_output.jpg

doc/img/vincent_van_gogh.jpg

doc/index.rst

doc/nitpick-exceptions.txt

doc/py_api.rst

doc/style_transfer.rst

doc/transfer_learning.rst

doc/user_guide.rst