Adding commandline override to env args to bin/messina.

```bash
$ bin/messina -h
Send log output to Loggins.
Usage: node ./bin/messina [opts]

Options:
  -g, --host      Overrides env["GRAYLOG_HOST"]    
  -p, --port      Overrides env["GRAYLOG_PORT"]    
  -f, --facility  Overrides env["GRAYLOG_FACILITY"]
  -h, --help      Print this help statement        
```

What do you think @jdotpz?