Initial pre-release

We have forked this repo from https://github.com/jasonlvhit/gocron, because as the readme notes - we haven't heard from Jason in a long time and want to keep the code progressing.

This is initial release provides some changes / updates to the way the prior code performed.

Added

• added the timeHelper interface to abstract the use of the time package and support future time mocking for testing

Changed

• the jobs array is now a slice
• the scheduling logic was transferred from the job handling scheduling itself to the scheduler handling scheduling of all jobs
• .From(gocron.NextTick) was changed to .StartImmediately
• moved StartAt into the scheduler
• the scheduler stopped chan uses an empty struct instead of a bool

Removed

• removed the default scheduler
• removed the mustInterval func - Second and Seconds provide the same behavior and are for grammar / semantics only at this point