Adding a default queue.

By default, Resque will try to work on the 'default' queue. Seems
simple.

I don't know how to write a good test for this, though.

lib/resque/cli.rb

@@ -18,7 +18,7 @@ def initialize(args = [], opts = [], config = {})
     end
 
     desc "work", "Start processing jobs."
-    option :queues,       :aliases => ["-q"], :type => :string
+    option :queues,       :aliases => ["-q"], :type => :string, :default => "default"
     option :require,      :aliases => ["-r"], :type => :string
     option :pid_file,     :aliases => ["-p"], :type => :string
     option :interval,     :aliases => ["-i"], :type => :numeric