Merge branch 'logits' into 'master'

bob/learn/tensorflow/dataset/__init__.py

bob/learn/tensorflow/dataset/image.py

bob/learn/tensorflow/dataset/siamese_image.py

bob/learn/tensorflow/dataset/triplet_image.py

bob/learn/tensorflow/estimators/Logits.py

bob/learn/tensorflow/estimators/__init__.py

bob/learn/tensorflow/examples/mnist/mnist_config.py

bob/learn/tensorflow/network/JointIncResV2Simple.py

bob/learn/tensorflow/network/SimpleCNN.py

bob/learn/tensorflow/test/test_estimator_onegraph.py

bob/learn/tensorflow/test/test_estimator_transfer.py

bob/learn/tensorflow/utils/util.py