Add ability to require other cljsfiddle namespaces.

[saolsen]

It'd be cool to write some cljsfiddle "library" fiddles and use them from a cljsfiddl "app" fiddle.

[jonase]

You can already do this. If it doesn't work it's a bug.

[saolsen]

Oh really, I just thought of it, didn't try it. Looks like it works, awesome! Thanks