simple JSON loader example for importing Clara.io JSON exports.

Over at the https://Clara.io project we constantly have people asking for simple examples for loading the JSON we export from Clara.io into ThreeJS.  To make things easier, we have both added documentation on our website here:

https://clara.io/learn/user-guide/data_exchange/threejs_export

And we have contributed the incredibly simple example in this PR for loading Clara.io JSON exports into ThreeJS.  I would like to expand on this example in the coming weeks, but this is a minimalist start.

My hope is that this will reduce people's troubles a lot.