ReadMe is misguiding

When I tried to configure the `socketProvider` as explained in the doc I got an error message `injector:modulerr`.

```
angular.module('myApp', [
'btford.socket-io'
]).
config(function (socketProvider) {
socketProvider.prefix('');
});
```

When I tried `socketFactoryProvider` instead, the `injector:modulerr` error seems gone but the `prefix` and other methods mentioned in readme are `undefined`. I found the doc misguiding. Am I doing something wrong, how can I get it work ??