Add random seeds to the training script
Add random seeds to the training script

This adds random seeds for NumPy and TensorFlow to the training script
to allow for reproducible experiments.  This work uncovered a potential
issue within TensorFlow in which non-determinism can occur with the
`tf.data.Dataset.map` function when `num_parallel_calls` > 1 and the
function body contains ops that make use of randomness, despite graph
and op-level seeds.  An issue has been opened, and hopefully
improvements will be made.  In the meantime, determinism can be achieved
by setting the `threads` to 1, at the cost of runtime performance.

Closes #8.

dusenberrymw/deep-histopath,dusenberrymw/deep-histopath