Add ability to update submodules before build

Update async write documentation

Remove ceiling on required protobuf version

Make possible lossy conversion explicit.

Add tox to Python build-from-source instructions.

Copyright  checker fixes

Add Cython files to check_copyright.py

remove stream from stalled_by_transport list before destroy it

fix one use of unreachable macro

Added exception handling for ImportError

Update copyrights

Add copyright checks to sanity; make them verify copyright year is valid

Happy new year

Initial style guide notes for C

This is possible now that https://github.com/google/protobuf/issues/855
is fixed (or at least appears to be fixed).

Add simple StartAndKillServer test

Update copyrights

Eliminate a layer of libraries in the end2end tests

Update link in credentials.h to point to grpc.io

Change CallData status before notifying CompletionQueue