Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- README.md
  discarded upstream changes
- app/controllers/api/v1/bookmarks_controller.rb
  finally merged upstream, some code style fixes
  and slightly changed pagination code
- app/controllers/application_controller.rb
  changed upstream to always return HTML error pages
  slight conflict caused by theming code
- app/models/bookmark.rb
  finally merged upstream, no real conflict
- spec/controllers/api/v1/bookmarks_controller_spec.rb
  finally merged upstream, slightly changed pagination code

spec/controllers/application_controller_spec.rb

@@ -22,11 +22,6 @@ describe ApplicationController, type: :controller do
   end
 
   shared_examples 'respond_with_error' do |code|
-    it "returns http #{code} for any" do
-      subject
-      expect(response).to have_http_status(code)
-    end
-
     it "returns http #{code} for http" do
       subject
       expect(response).to have_http_status(code)