Accurately get the number of batches.

iterations.md

for batch in range(num_data // batch_size + (num_data % batch_size > 0)):

Ever run into errors when training models that have to do with running one too many or two few batches?

This snippet should fix it.

1. First get the number of iterations that the batch fits cleanly in the number of data points. E.g. num_data // batch_size.
2. Add 1 if there are remaining data points. E.g. (num_data % batch_size > 0)1.

This does assume python3.