Add support for subtitle and sound in terminal-notifier.

lib/notifier/terminal_notifier.rb

@@ -12,9 +12,14 @@ def notify(options)
         "-group", "notifier-rubygems",
         "-title", options[:title].to_s,
         "-appIcon", options.fetch(:image, "").to_s,
-        "-message", options[:message].to_s
+        "-message", options[:message].to_s,
+        "-subtitle", options.fetch(:subtitle, "").to_s
       ]
 
+      # -sound with an empty string (e.g., "") will trigger the
+      # default sound so we need to check for it.
+      command.concat(["-sound", options.fetch(:sound, "default").to_s] ) if options[:sound]
+
       Thread.new { system(*command) }.join
     end
   end