Merge pull request marcinc#5 from EqualMedia/optional-block

only yield if block given when getting next start_time

Merge pull request marcinc#4 from EqualMedia/params-guard

args expected type guard

Merge pull request marcinc#3 from EqualMedia/fix-load-order

fixes load order issue

Merge pull request marcinc#2 from EqualMedia/sleep-fix

sleep time fix

Merge pull request marcinc#1 from EqualMedia/initial-version

initial version