Removing rake completion from lib/ as it was moved to rails plugin

lib/rake_completion.zsh

-function _cap_does_task_list_need_generating () {
-  if [ ! -f .cap_tasks~ ]; then return 0;
-  else
-    accurate=$(stat -f%m .cap_tasks~)
-    changed=$(stat -f%m config/deploy.rb)
-    return $(expr $accurate '>=' $changed)
-  fi
-}
-
-function _cap () {
-  if [ -f config/deploy.rb ]; then
-    if _cap_does_task_list_need_generating; then
-      echo "\nGenerating .cap_tasks~..." > /dev/stderr
-      cap show_tasks -q | cut -d " " -f 1 | sed -e '/^ *$/D' -e '1,2D'
-> .cap_tasks~
-    fi
-    compadd `cat .cap_tasks~`
-  fi
-}
-
-compctl -K _cap cap