Version pinning in requirements.txt

[KevOrr]

Is there any reason that the protobuf dependency in requirements.txt is pinned to 3.6.1? This is very odd for libraries, since it will cause conflicts if other libraries require for e.g. >=3.7.

I noticed that the dependency for grpcio was recently changed so that its version isn't pinned anymore (#51). Is there some reason that protobuf stayed pinned?

Thanks

[danielmai]

I can't think of any good reasons to pin protobuf. We should unpin it like we did with grpcio.