Heavily based on SegDataGenerator (https://github.com/aurora95/Keras-FCN/blob/master/utils/SegDataGenerator.py), with a variety of updates to add python 3, and keras >= 2.0 compatibility.
A Usage example can be seen in the test notebook.
- Add an option to pass is a list of the classes that binary images shoudl be transformed into.