Cron parser should not support jobs scheduled in seconds

[utsavk1993]

Ideally, Cron job cannot be used to schedule a job in a seconds interval. Can you provide an option to disable it and throw an error if some user schedules the job in seconds E.g. */30 * * * *

[harrisiirak]

@utsavk1993 it sounds like a reasonable addition.

[harrisiirak]

I'll close it in favour of https://github.com/harrisiirak/cron-parser/issues/249 (optionally disabling cron extensions)