Performance page should state which version of each tool was tested

[fingolfin]

The page https://sift-tool.org/performance compares performance to grep (presumably GNU grep? please clarify!), ack, ag, and pt. But it does not state which version of these. Now there has been a lot of activity for all of the tools (thanks to the healthy competition, to which also sift contributes). So reading that page, one is left to wonder which version of each tool was tested.

It would hence be great to add that information. Also, ideally, the date on which the comparison was made, which also helps readers to roughly judge how up-to-date it is.

Thank you for creating sift!