Move to different proto engine about pogom

[bas-stringer]

The python library Google provides comes with a C++ backend that's disabled by default, but delivers significant speedups if switched on (which may or may not be straightforward on different platforms). Even so, Pyrobuf claims to outperform it regardless:

https://github.com/appnexus/pyrobuf
http://techblog.appnexus.com/blog/2015/12/22/pyrobuf-a-faster-python-protobuf-library-written-in-cython/

It's hard to compare these alternatives in terms of performance or ease of deployment/distribution, but pyrobuf appears to me as the most mature project of the bunch.

[nborrmann]

Thanks for the tip. I had a look at it, but it turns out:

• It doesn't support nested types (appnexus/pyrobuf#56). Maybe we can restructure our proto definitions accordingly?
• It's hard to install on windows, as it needs cython and a c++ compiler