Merge branch 'master' of github.com:google/grpc

include/grpc++/server_credentials.h

include/grpc/grpc_security.h

src/core/security/credentials.c

src/core/security/credentials.h

src/core/security/security_context.c

src/core/security/security_context.h

src/cpp/client/credentials.cc

src/cpp/server/server_credentials.cc

src/node/binding.gyp

src/node/credentials.cc

src/node/server_credentials.cc

src/php/ext/grpc/credentials.c

src/php/ext/grpc/server_credentials.c

src/ruby/ext/grpc/extconf.rb

src/ruby/ext/grpc/rb_credentials.c

src/ruby/ext/grpc/rb_server_credentials.c

test/core/end2end/data/prod_roots_certs.c

test/core/end2end/data/server1_cert.c

test/core/end2end/data/server1_key.c

test/core/end2end/data/ssl_test_data.h