No longer using c2.unify, which also means we can use sablono instead of...

... chart-html

So looks like #1138 was a result of the [dangerouslySetInnerHtml](https://github.com/onaio/zebra/compare/1138_charts_immediately_on_add?w=1&expand=1#diff-8288ee4804d2df65aa865bb06429054eL97) that was used for the charts. I have removed the use of `c2.unify`, which means that we can use `sablono/html`, and no longer need to use `dangerouslySetInnerHtml`, which is great.

I will also take this opportunity to deprecate / remove `ona.utils.charts/chart-html` (mostly used in the tests at the moment), but making this pull request in advance of the deprecation so that Monday's release can go through with non-broken charts.