Merge remote-tracking branch 'google/release-0_13' into merge-and-regen

PYTHON-MANIFEST.in

grpc.gemspec

requirements.txt

src/ruby/lib/grpc/version.rb

templates/grpc.gemspec.template

templates/src/ruby/lib/grpc/version.rb.template

test/distrib/csharp/run_distrib_test.sh

test/distrib/node/run_distrib_test.sh

test/distrib/python/run_distrib_test.sh

third_party/rake-compiler-dock/Dockerfile

third_party/rake-compiler-dock/build.sh

...uild/patches/rake-compiler-0.9.5/compat-with-bundler.diff

tools/buildgen/plugins/expand_version.py

tools/jenkins/docker_run.sh

tools/run_tests/artifact_targets.py

tools/run_tests/build_artifact_node.sh

tools/run_tests/build_package_node.sh