Early on I played with adding a type field to requestSession. Something like...

```coffee
requestSession 'default_media_receiver', -> #callback
requestSession 'stylized_media_receiver', -> #callback
requestSession 'custom_receiver', -> #callback
```
...or something

The purpose being to initialize and return either a `MediaSession` ('default_media_receiver' or 'stylized_media_receiver') or a `CustomSession` ('custom_receiver') object. Message passing has no effect when using the default/stylized media receiver. Was thinking functions related to message passing on `Session` could be moved to a new `CustomSession` class. Also this new `CustomSession` class would not return a `MediaControls` object nor would it emit play, pause, stop, seek events.  

...some randoms, don't think it blocks getting this in though!