Update fedora

[kasicka]

Update guidelines for installing from Fedora repositories

[fhemberger]

/cc @nodejs/build please review.

[jbergstroem]

We have a testing gap for fedora25 in CI and still support fedora22 (which probs should be dropped) -- not sure how to handle this but otherwise LGTM.

[kasicka]

I thought that was more about what is available from Fedora repositories, which is responsibility of Fedora packagers.

[jbergstroem]

Upon reading the full page, the responsibility is pushed back to package maintainers but the word "supported" is ambiguous. Anyway, don't let me hold up progress.

[fhemberger]

@kasicka @jbergstroem Sorry for the long delay: Can this be merged? If the range of supported versions/platforms is managed by the Fedora package maintainers, should we remove the list entirely?

[fhemberger]

Merging this now … if the supported Fedora version range changes (or should be removed entirely), please open a new PR.