Implement a generic 204 response

[alexburley]

We should implement a generic 204 response something like 'success: true' or something, commonly used by upload calls, delete calls etc.

Maybe falafel should provide this by default..

[Ryanbarker0]

Perhaps this method can take a key name as an arg and always return a { [key]: true }. That way we can set the value to be anything from updated: true, success: true, deleted: true etc.

@alexburley Thoughts on this?