fix build and config_spec

lib/crono/config.rb

@@ -13,7 +13,6 @@ module Crono
     def initialize
       self.cronotab = CRONOTAB
       self.logfile  = LOGFILE
-      @pidfile = PIDFILE
       self.piddir = PIDDIR
       self.process_name = PROCESS_NAME
       self.daemonize = false

spec/config_spec.rb

@@ -8,7 +8,6 @@ describe Crono::Config do
       @config = Crono::Config.new
       expect(@config.cronotab).to be Crono::Config::CRONOTAB
       expect(@config.logfile).to be Crono::Config::LOGFILE
-      expect(@config.pidfile).to be nil
       expect(@config.piddir).to be Crono::Config::PIDDIR
       expect(@config.process_name).to be Crono::Config::PROCESS_NAME
       expect(@config.daemonize).to be false