Render <noscript> contents to string

This is the fix for #1252; it uses `renderComponentToStaticMarkup` on the children so that the server and browser both treat them the same (as text content). In browsers that have JS disabled…well, React won't be loaded so it can't be upset that the contest are actual nodes :stuck_out_tongue_closed_eyes:

Let me know if any improvements can be made. I didn't see a `map` utility for the children list that produced an array so I used `ReactChildren.forEach`. I think the tests cover everything, but if not, let me know!