Proto commits in hubo1016/aiogrpc

These 2 commits are when the Protocol Buffers files have changed:

Commit:f1cdad9
Author:Gustavo Carneiro
Committer:Gustavo Carneiro

add test case showing "Future exception was never retrieved" on async gen

The documentation is generated from this commit.

Commit:b8f5393
Author:hubo

bug fixes and tests