Add pidfile option

lib/crono/config.rb

@@ -2,14 +2,17 @@ module Crono
   class Config
     CRONOTAB  = "config/cronotab.rb"
     LOGFILE   = "log/crono.log"
+    PIDFILE   = "tmp/pids/crono.pid"
 
     attr_accessor :cronotab
     attr_accessor :logfile
+    attr_accessor :pidfile
     attr_accessor :daemonize
 
     def initialize
       self.cronotab = CRONOTAB
       self.logfile  = LOGFILE
+      self.pidfile  = PIDFILE
       self.daemonize = false
     end
   end