Improve documentation, add sample config and readme.

serialboard.rb

@@ -26,12 +26,14 @@ serial_posts.sort! { |x,y| y.time <=> x.time }
 domains = []
 serial_posts.each do |post|
   metric[:posts] += 1
+  # Extract the domain from the full URL
   domain = post.href.sub(/^https?:\/\/(.*?)\/.*$/, "\\1")
 
   if !domains.include? domain
     # Record that we've seen the domain now.
     domains.push domain
   else
+    # If this is a duplicate, soft-delete it.
     post.tag.delete config['active_tag_name']
     post.tag.push config['deleted_tag_name']
     post.shared = false