segmentation and FCN training examples + class

[ahundt]

We have models for segmentation including DenseNetFCN, but we need a training example.

I've tested Keras-FCN. It works well as a starting point, and the author is happy to see it incorporated into keras-contrib. I also have a fork with DensenetFCN and #46 integrated.

A few questions before a pull request is created:

1. Is there interest in this?
2. Where would be the appropriate place and manner to integrate SegDataGemerator, which performs training/augmentation on segmentation data?
3. What about auxiliary functions such as conversion of pretrained weights, perhaps that should go directly in the example script?

[ahundt]

segmentation_keras is another repository that has less functionality than Keras-FCN, but the code is a bit cleaner.