h2load against gRPC greeter_server

sample.rst

command-line:

$ h2load http://localhost:50051/helloworld.Greeter/SayHello \
      -d grpc-upload \
      -H 'te: trailers'
      -H 'content-type: application/grpc'
      -n1000000 -c100 -m100

Create grpc-upload file using following python script:

d='\x00\x00\x00\x00\x07\x0a\x05\x77\x6f\x72\x6c\x64'
with open('grpc-upload', 'w') as f: f.write(d)