Freeze grpcio for stability.

[miott]

Let's pin grpcio to a specific version in setup.py. We can monitor it for important fixes or new features and then upgrade after analysis of backward compatibility and stability.

[remingtonc]

Addressing in pin-grpc.

[remingtonc]

A potential thought - I have heard that "libraries" generally shouldn't pin dependencies. The applications should pin the dependencies. This is why none of the library dependencies are pinned. Do you agree with this philosophy? Legitimately don't have a full opinion.

[miott]

Not sure what this is referring to but where do you draw the line between a "library" and an "application"?

Have seen it cause issues and save headaches. What many have ended up doing was using >= the version you know works and < the next major version. If the author is following basic versioning semantics, a major version change means something from the previous version will not work.