Merge to Master Checklist

[madisonmay]

• [ ] Tests
• [ ] Documentation (readme.io? inline?)
• [x] Cost functions class interface (like updates and regularization) with default
• [x] Auto-intuit best cost function for highest layer of net (cce = softmax, mse = linear, etc...)
• [ ] knn.py
• [ ] inspect internal state (look at activation)
• [x] stopping functions class interface (like updates and regularization) with default
• [ ] CNN