Merge pull request #1 from fruitschen/master

avoid being stuck by adding pid check
Use a default value for CRON_PID_FILE if one isn't set.
Merge pull request #2 from fruitschen/master

added the cron management command to reset the executing flag
Remove obselete MAX_REQUESTS info
Added requeue script.
removed useless comment
added an output for field being used as string
Merge pull request #3 from radiosilence/master

Requeue functionality
Discard the seconds to prevent drift. Thanks to Josh Cartmell
Change crontab finished message to include the current time.
and tweak the wording a little
Make the comment match the `run_every` attribute
Merge pull request #4 from peterbe/patch-1

Make the comment match the `run_every` attribute
fix bug: Code will fail in django 1.4 or later as user.message_set is no longer available