Merge pull request #3558 from murgatroid99/node_auth_plugin

binding.gyp

src/node/ext/call.cc

src/node/ext/call.h

src/node/ext/call_credentials.cc

src/node/ext/call_credentials.h

src/node/ext/channel.cc

src/node/ext/channel_credentials.cc

src/node/ext/channel_credentials.h

src/node/ext/node_grpc.cc

src/node/index.js

src/node/interop/interop_client.js

src/node/performance/perf_test.js

src/node/performance/qps_test.js

src/node/src/client.js

src/node/src/credentials.js

src/node/test/call_test.js

src/node/test/channel_test.js

src/node/test/credentials_test.js

src/node/test/end_to_end_test.js

src/node/test/health_test.js