Data processing tutorial

[goodboy]

I'd like to hash out a set of examples for how a real-time data processing pipeline could be designed with tractor.

My initial though was a streamer feeding 2 processors which each do frame oriented numpy array processing (say a linear regression and some statistics err sumthin) and and ship the results to a parent with all actors using async generators for the frame delivery.

msgpack-numpy should take care of the serialization easy peasy.