storage doc fix

storage overview docs at http://googlecloudplatform.github.io/gcloud-node/#/docs/v0.13.2/storage reference

```
var bucket = gcloud.storage.bucket('my-bucket');
```

and should be 

```
var bucket = gcloud.storage().bucket('my-bucket');
```
