Multiple koa-views middlewares
Is it possible to use multiple koa-views middleware objects in one application? Adding it once within app like below works. 

`
app.use(views(__dirname + '/views', {
    map: {pug: 'pug'},
    extension: 'pug'
}));`

However, when I add another instance of the middleware but pointing to another directory, it cannot find the views from the latter. In this example koa-views doesn't even look in _/admin/views_ directory. It 'encouters' the first koa-views middleware, does not find a matching view in _/views_, and stops.

```
app.use(views(__dirname + '/admin/views', {
    map: {pug: 'pug'},
    extension: 'pug'
}));
```

How do I make koa-views continue searching for files if there are multiple middleware instances and the first one does not find the requested view?

Thanks
