minimal "browser first" testing library + test reporter

[serapath]

@todo

• [ ] minimal "browser first" testing library + test reporter

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it should run tests in an iframe and report to the parent window which will render test results

[serapath]

• maybe related (maybe not) https://github.com/ethereum/play/issues/75

[serapath]

The reporting should also include test coverage in a similar style to https://github.com/ethereum/play/issues/78