Create a quick way to measure performance

[gijsk]

This is a pretty bare-bones approach, but it spits out two numbers and that seems useful enough as a baseline. @leibovic, @n1k0 - thoughts?

[DavidBruant]

2 numbers aren't enough to be meaningful (on my machine, Readerized everything, took 286ms., yes, but for 1 file ? 10 ? 100 ?). At least print out the number of processed HTML files.
With fast-stats, you can very easily get the mean/median/sum of a serie of values.

For high-precision time measurement (not Date.now() specialty), you can use process.hrtime()

[gijsk]

The noise is in the 1-2ms ballpark on my machine, so it doesn't seem useful to get more high-precision measures.

My usecase is "how much does patch X slow this down", for which the current state is fine.

I selected the "real" articles from our existing testcases, so I don't think mean/median is useful as they are different files.

[gijsk]

The process.hrtime() doesn't seem to improve noise levels much for me, but perhaps on slower machines it'll help, so let's go with that.

[gijsk]

Closing in favour of #90 .