Merge branch 'issue_43' 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/tfrecords.py

bob/learn/tensorflow/dataset/triplet_image.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/loss/TripletLoss.py

bob/learn/tensorflow/loss/__init__.py

bob/learn/tensorflow/test/test_cnn.py

bob/learn/tensorflow/test/test_cnn_pretrained_model.py

bob/learn/tensorflow/test/test_cnn_scratch.py

bob/learn/tensorflow/test/test_dataset.py

bob/learn/tensorflow/test/test_estimator_onegraph.py

bob/learn/tensorflow/test/test_estimator_triplet.py

bob/learn/tensorflow/utils/util.py