Update or remove outdated and broken links as appropriate

[dobey]

Fixes #29

[KAMiKAZOW]

Can we use Plasma Mobile's Matrix room for the old IRC link? #plasmamobile:kde.org / https://webchat.kde.org/#/room/#plasmamobile:kde.org (with the approval of KDE, of course)

Most current contributors hang out there anyway.

[dobey]

Can we use Plasma Mobile's Matrix room for the old IRC link?

I think it might be better to create a more neutral chat group for it instead, especially once I get the current lomiri-keyboard replaced in Ubuntu Touch and we start getting more contributions from other platforms using Maliit. The READMEs and web site(s) also need a bigger change at this point, which can be done in a later change.