Anomaly modular

1/ turn `anomaly.py` into a class for better reuse, move related logic from `clamodel.py` here
2/ nice speedup for python (use `numpy.sum()`)
3/ new features/"implementation" to anomaly computation - parametrized, default off, so no change from current 
3.1/ new `cumulative anomaly` (sliding window)
3.2/ @subutai Please have a look if you like this approach, it's prepared for integration with your `likelihood` anomaly code
4/ added tests
Do we need these "enum"s?  Looks like the user is just passing in the raw string, not the constants. Why not just use the raw string everywhere?  It would be simpler.