setup.py

(1) Move dependency on protobuf from grpcio to grpcio_test. While the
most-commonly-foreseen use case of grpcio makes use of protobuf,
technically protobuf is not strictly needed and there's no actual
in-code relationship between grpcio and protobuf.

(2) Loosen the dependency on protobuf from ==3.0.0a3 to >=3.0.0a3.

(3) Update all references to 0.10.0* to 0.11.0.

(4) Alphabetize the grpcio_test dependencies.