Add defaults to `rails server -h`

It seems like on calling rails server -h, those defaults values are left blank:

Sikachus-Notebook:test_edge sikachu$ rails server -h
Usage: rails server [options]
    -p, --port=port                  Runs Rails on the specified port.
                                     Default:
    -b, --binding=ip                 Binds Rails to the specified ip.
                                     Default:
    -c, --config=file                Use custom rackup configuration file
    -d, --daemon                     Make server run as a Daemon.
    -u, --debugger                   Enable ruby-debugging for the server.
    -e, --environment=name           Specifies the environment to run this server under (test/development/production).
                                     Default:

    -h, --help                       Show this help message.
Exiting

It seems like options hash that passed to OptionParser.new is empty, so those defaults would just left blank. I saw that in Rack::Server they actually hardcode the default values, so I think it would be ok to hard-code those data in here too.