Clarify meaning of @every

Fixes issue robfig#104

Author: robfig

doc.go

@@ -84,16 +84,16 @@ You may use one of several pre-defined schedules in place of a cron expression.
 
 Intervals
 
-You may also schedule a job to execute at fixed intervals.  This is supported by
-formatting the cron spec like this:
+You may also schedule a job to execute at fixed intervals, starting at the time it's added 
+or cron is run. This is supported by formatting the cron spec like this:
 
     @every <duration>
 
 where "duration" is a string accepted by time.ParseDuration
 (http://golang.org/pkg/time/#ParseDuration).
 
-For example, "@every 1h30m10s" would indicate a schedule that activates every
-1 hour, 30 minutes, 10 seconds.
+For example, "@every 1h30m10s" would indicate a schedule that activates immediately,
+and then every 1 hour, 30 minutes, 10 seconds.
 
 Note: The interval does not take the job runtime into account.  For example,
 if a job takes 3 minutes to run, and it is scheduled to run every 5 minutes,