Add option for static render

[noahlh]

Several have suggested this and it's a good idea: We should add an option to celestite_render() to allow for a static render in production, which is to say, avoid a r/t to the Node server.

This will be for certain pages whose content we can reliably expect to be static / pre-rendered. If there's no crystal variables being sent (eg no DB calls, etc.) and no server-side node requirements, then we can simply serve up the pre-rendered HTML.