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

Conflicts:
	README.md
	app/controllers/statuses_controller.rb
	app/lib/feed_manager.rb
	config/navigation.rb
	spec/lib/feed_manager_spec.rb

Conflicts were resolved by taking both versions for each change.
This means the two filter systems (glitch-soc's keyword mutes and tootsuite's
custom filters) are in place, which will be changed in a follow-up commit.

app/validators/email_mx_validator.rb

@@ -16,6 +16,8 @@ class EmailMxValidator < ActiveModel::Validator
     return true if domain.nil?
 
     records = Resolv::DNS.new.getresources(domain, Resolv::DNS::Resource::IN::MX).to_a.map { |e| e.exchange.to_s }
+    records = Resolv::DNS.new.getresources(domain, Resolv::DNS::Resource::IN::A).to_a.map { |e| e.exchange.to_s } if records.empty?
+
     records.empty? || on_blacklist?(records)
   end