Allow any root node?

[EvanSimpson]

Right now the library only allows the root node to be an object or an array node, and any other value renders empty. Is this intentional, or would it be helpful to be able to display any value as the root node (surely at the very least adding capability for a JSONIterableNode as root)?

[EvanSimpson]

I managed to implement this with a small modification to grab-node.js and then using that to pick the root node in index.js on this branch.

Happy to open a PR if this is desirable to others.

[chibicode]

@EvanSimpson Hi Evan, thank you for pointing this out! I tracked it down to the original source code on Bitbucket: https://bitbucket.org/davevedder/react-json-viewer/commits/8b168f18ffd5bb53882793038a4994eeafe40b0f#Lsrc/jsx/jsonViewer.jsxT331 and this hasn't changed since. I don't see a downside in allowing any root node - reusing grab-node.js seems like a reasonable thing to do.

I just pulled in your changes :)