Spike: Evaluate options for testing library injected DOM

Working with external, non-react, libraries is a pain in the react ecosystem; testing is no exception. We should see if there is anything we can do, to normalize the DOM that gets injected by third party libraries.

React's TestUtils do not currently support this, so it'd be a huge win if enzyme _could_.

Highcharts is a decent test library.

Start by reviewing React's TestUtils limitations for DOM injected by external libraries and use Highcharts as the concrete evaluation case. Determine whether Enzyme can normalize that injected DOM, then document the viable options and their trade-offs as the completed spike.

Written by the indexing model from the issue text.