add option[:at]
Merge branch 'develop' of github.com:sellect/delayed_cron into feature/option-at

* 'develop' of github.com:sellect/delayed_cron:
  add gitignore
update readme for option[:at]
update readme
update readme
make seconds option for option[:at]
update readme
fix option[:at]
Merge branch 'feature/option-at' into develop

* feature/option-at:
  fix option[:at]
  update readme
  make seconds option for option[:at]
  update readme
  update readme
  update readme for option[:at]
  add option[:at]