Default port should be 27017

[benmccann]

If I specify a "host", but not a "port" then it seems to default the port to 0. I think it'd be good to make the default port 27017

"servers":
    [
      { "host": "107.59.235.144" },
      { "host": "107.59.235.146" }
    ]

[benmccann]

Thanks for the fix!!