Investigate using the speedracer library to run benchmarks

[markerikson]

Over in reduxjs/react-redux#983, @sebinsua pointed to https://github.com/speedracer/speedracer as a relevant tool for running benchmarks like this and reporting results. It looks very interesting, but also seems lacking in soem capabilities we would want. Worth investigating, though - maybe we could either push some updates to it, or fork it.

Related: I'd really like to see some +- changes in metrics calculated automatically somehow.