Create bindings for Vega and Vega-Lite

[teodorlu]

Basis for this PR is an attempt to use Shadow-CLJSJS to build a project that makes use of Oz. Oz uses Vega and Vega Lite for visualization. For more details, see the issue. Credit for this work is to @ivanminutillo.

@thheller, does this look right to you? I don't have a lot of Clojurescript experience, and I'd be happy to get a second pair of eyes.

[thheller]

Looks good to me. Assuming this actually works?

[teodorlu]

It works when I put the files directly on the classpath (example). I haven't tested running Shadow-CLJS with a version of shadow-cljsjs that includes these changes.

I hope to be able to remove the cljs/{vega,vega_embed,vega_lite,vega_tooltip}.cljs files when these changes reach Shadow-CLJS. I assume that happens when you've bumped the versions of shadow-cljsjs and shadow-cljs?

[thheller]

I already released [thheller/shadow-cljsjs "0.0.18"] so you can bump that. I'll make a new shadow-cljs release soon that'll include that dep.

[teodorlu]

Sounds great! I'll test now.

[teodorlu]

Works like a charm! See diff for the example project.

[jamiepratt]

I think the correct symbol name to export from vega-lite is vegaLite not vl. Hanami is trying to call vegaLite.

#20