Allow to pass the constructor replica sets for mongoskin.

When trying to pass a replica set configuration to mongoskin through the constructor it failed before. Now this is possible:


```js
var db = livedbMongo(['localhost:27107', 'localhost:27108'], {database: 'sharejs'});
```

For an example from mongoskin see [here](https://github.com/kissjs/node-mongoskin/blob/master/examples/replSetBenchmark.js)