asyncRender, but any wrapping of the function in a request
context is expected to be done before
renderFunction is passed to this,
asyncRender takes care of the wrapping for you.
If you're going to be managing the asynchronicity of the render externally (e.g., with futures), call this when you're ready to render your results and the rendering will be sent down to the client.
If you're going to be managing the asynchronicity of the render externally, make sure to call this so that the async plumbing will be set up on the page when it gets sent down.