So how would supporting both work? Would a single look like the following? :

````
on_content_change:
    strategy: foobar
    options: { }
````

If you agree with the format in this PR for "on_content_change" I prefer to not do any more work on Configuration in this PR - so it can be focussed on the `content_change` event. There is #38 which has a proposition for a new configuration format - perhaps we can work on that?