Try out an idea for highlighting elements.

Isn't going to work - I don't think this can be done in CSS.
Take a different tack. Seems to sort of work.

Will need a good bit of testing.
Escape values.
Merge branch 'feature/copy-output' into develop
Render ArraySeqs. Fixes #67.
Rename vega, html etc to to as-*. Fixes #63.
Bump version to 0.2.0-SNAPSHOT.
Better handling of failed initial save. Fixes #53.