Update tutorial.md (#721)
Update tutorial.md (#721)

changed http://localhost:3000/hello_world to http://localhost:5000/hello_world
shakacode/react_on_rails,szyablitsky/react_on_rails,szyablitsky/react_on_rails,shakacode/react_on_rails,shakacode/react_on_rails,shakacode/react_on_rails,szyablitsky/react_on_rails,shakacode/react_on_rails,szyablitsky/react_on_rails