Update docs for "apply" and add an example
Update README.md to new constructors
Fixed testConcurrentOnNextFailsValidation
Merge pull request #1239 from zsxwing/apply-scaladoc-example

Update docs for "apply" and add an example
Merge pull request #1248 from akarnokd/SchedulerTestConcurrentFix

Fixed testConcurrentOnNextFailsValidation