2.1.1

Bugfix

• Grav 2.0 sites can update to 2.1. bin/gpm selfupgrade treated each minor release as a separate line, the way 1.7 and 1.8 were, so a 2.0 site was told it was up to date while 2.1.0 was out. Only a new major version now needs a manual move #4299
• When a new major version of Grav is out, bin/gpm selfupgrade says so and links to the migration guide instead of only reporting that the site is up to date