http browserify broken when sending a full node url object

```
var url = {
host: "localhost:8081",
hostname: "localhost",
href: "http://localhost:8081/api/foo?bar=baz",
method: "GET",
path: "/api/foo?bar=baz",
pathname: "/api/foo",
port: "8081",
protocol: "http:",
query: "bar=baz",
search: "?bar=baz",
slashes: true
};
var request = http.get(url, noop);
```

```
expected: "http://localhost:8081/api/foo?bar=baz"
actual: "http://localhost:8081:8081/api/foo?bar=baz"
```

The url that is requested has the port in it 2 times. This is because of this line.
https://github.com/substack/http-browserify/blob/master/index.js#L7

I am finishing up a pull request to fix this where it will try host first, then hostname+port.

Please let me know if you have any input.