add additional documentation for wait for schedule (#551)

README.md

@@ -39,6 +39,14 @@ if err != nil {
 	// handle the error related to setting up the job
 }
 
+// to wait for the interval to pass before running the first job
+// use WaitForSchedule or WaitForScheduleAll
+s.Every(5).Second().WaitForSchedule().Do(func(){ ... })
+
+s.WaitForScheduleAll()
+s.Every(5).Second().Do(func(){ ... }) // waits for schedule
+s.Every(5).Second().Do(func(){ ... }) // waits for schedule
+
 // strings parse to duration
 s.Every("5m").Do(func(){ ... })
 

scheduler.go

@@ -550,7 +550,10 @@ func (s *Scheduler) EveryRandom(lower, upper int) *Scheduler {
 // parses with time.ParseDuration().
 // Valid time units are "ns", "us" (or "µs"), "ms", "s", "m", "h".
 //
-// The job is run immediately, unless StartAt or At is set.
+// The job is run immediately, unless:
+// * StartAt or At is set on the job,
+// * WaitForSchedule is set on the job,
+// * or WaitForScheduleAll is set on the scheduler.
 func (s *Scheduler) Every(interval interface{}) *Scheduler {
 	job := s.getCurrentJob()