Aurelia custom element async life cycle event

I saw a really good conversation in the Aurelia/framework Github issue queue that I wanted to save for later.  https://github.com/aurelia/framework/issues/367#issuecomment-198104416

From Rob Eisenberg:

We can't provide this (async promise life-cycle events) across all components. It would be a disaster for performance and would no longer map in any way to web components. 

If you don't care about web components, you can use the new CompositionTransaction: http://aurelia.io/docs.html#/aurelia/templating/1.0.0-beta.1.1.2/doc/api/class/CompositionTransaction 

Simply have that injected into your component constructor and then call enlist() this will return you a CompositionTransactionNotifier: http://aurelia.io/docs.html#/aurelia/templating/1.0.0-beta.1.1.2/doc/api/interface/CompositionTransactionNotifier 

You can call done on that when your async operation is complete. The global composition will wait to attach until after you are done.

How do I wait for async data for an Aurelia custom element?