Start work on new renderer.
Plumb in renderer as nREPL middleware.

Also, start to work on client side.
More work on new renderer, starting to work now.
Work on Vega rendering.

Some nasty stuff in this commit that needs to be reorganised.
Cleanup, latex, error handling.
More work on renderer, add tables.

Seems to work pretty well now. Needs some code cleanup in
list-like/table renderer.
Add html output type. Long handling.
Center table and plot.
Merge branch 'develop' into feature/new-renderer
Fallback for renderer failure.
Document "double JSON" workaround.
Add plain text render type.
Merge branch 'develop' into feature/new-renderer
Code cleanup, support more types.
Break out Renderable protocol into own project.

Add the last few built-in type renderers.
Tweak styling.
Tweak colour scheme.