New smiley middleware with configurable faces.

See: https://app.getflow.com/workspaces/230825/tasks/10155617

Now there is middleware for smileys. You can use it by going:

```javascript
var smile = require('./lib/smile');
smile({ smile: ':<' });
```

Since people might want to change the face there is a configuration option for setting it.
Merge pull request #1 from izaakschroeder/smiley-faces

Adds more happiness to the homepage including happy and sad face.