A lot of new features

• 905ffc94 small changes: nit, bug fix, small features
• 214fad7a Add scripts for training keras models using keras API
• 13ae3919 Add two functions to allow dynamic weighting of samples per batch
• c77e386e Add several extractors which are usefull at inference time
• 0b0055bf Add a generic Generator class alternative to BioGenerator
• 18e34e61 Add virtual adversarial training loss
• fcc10424 Fix the euclidean function so that its gradients don't become nan. Also moves the bytes_to_human function
• 5ad23cfd Add a hook to add some tensors to the summary
• 9f3b752b Add bob tf predict command
• 09edcdf7 Fix the image augmentation function
• 9921e122 Add dataset_to_tfrecord and dataset_from_tfrecord
• c3c9e9a1 Make bob tf cache command useful
• 316eca76 Add a new MLP architecture
• 6809b360 Fixes in inception architectures
• 0ab7c214 setup.py required changes for multiple features