Fixed 2.0.0 regression in NoThreadScheduler with adding tasks that already have tasks of the same delay in them
Because the clock may advance for getting the delay of existing tasks, we need to be willing to check <= and not just == when finding the insertion index.  That way we are ensure that new tasks are added after existing tasks with the same expected delay.

I also added javadoc to the protected .tick() to indicate it is NOT thread safe