Add sync command for neo4j, fix configuration, add neo4j to docker-compose, fix seed

lib/tasks/mastodon.rake

@@ -41,4 +41,11 @@ namespace :mastodon do
       $redis.keys('feed:*').each { |key| $redis.del(key) }
     end
   end
+
+  namespace :graphs do
+    desc 'Syncs all follow relationships to Neo4J'
+    task sync: :environment do
+      Follow.find_each(&:sync!)
+    end
+  end
 end