JSFiddle export

[davidbau]

A Pencil Code program is almost exactly the same as what can be expressed in JSFiddle. We should allow students to export their work to JSFiddle, probably through the "share" button.

JSFiddle has a POST API that should allow us to do this from the browser, and they recently fixed an issue that should allow us to post a coffeescript program.

jsfiddle/jsfiddle-users#532

The POST API is described here:

http://doc.jsfiddle.net/api/post.html

[davidbau]

Note that #152 is a PR from Katie Dektar that begins this work.