Add versions to the referenced software

[DeaMariaLeon]

When we add content to Tools collection, maybe we should add the dates and/or versions of the software we are mentioning.

As we know, software changes very often. We may be recommending something that has already changed or that is not relevant anymore. For example gitpod for pandas development needed updates at some point (in pandas' code). I doubt that it has been done.

Maybe there should be a template or contribution instructions on how to add something to the tools section.

[InessaPawson]

@DeaMariaLeon Adding a version of the referenced software is a great idea.

Creating contribution guidelines for the Tools section would be useful. Please submit a PR if you have suggestions.

[InessaPawson]

Addressed in #97.