Add ClojureScript code coverage

[lvh]

All ClojureScript code is tested, but we don't measure our test coverage. This is primarily due to a limitation in cloverage. We should test both and merge the results.

[lvh]

Another way for us to do this may be through source maps + remap-istanbul/istanbul-coverage-source-map.

see: https://www.sitepen.com/blog/2015/09/29/code-coverage-for-typescript-and-other-transpiled-languages/