Revert "Fixed issue #19 'Rake not auto completing'. The stat command syntax...

Revert "Fixed issue #19 'Rake not auto completing'.  The stat command syntax that was being used was not correct. Or at least on my machine.  See man page for the stat command"

This reverts commit 83907294.

lib/rake_completion.zsh

 _rake_does_task_list_need_generating () {
   if [ ! -f .rake_tasks~ ]; then return 0;
   else
-    accurate=$(stat -c "%n" .rake_tasks~)
-    changed=$(stat -c "%n" Rakefile)
+    accurate=$(stat -f%m .rake_tasks~)
+    changed=$(stat -f%m Rakefile)
     return $(expr $accurate '>=' $changed)
   fi
 }