Previously this a tool in `plot.R`. It is now are more complete tool
which executes the benchmarks many times and creates a boxplot.
PR-URL: https://github.com/nodejs/node/pull/7094
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
