Implement main, optional seconds, and from file

scheduler/scheduler_test.go

@@ -75,6 +75,10 @@ func TestSchedulerFromFile(t *testing.T) {
 			content: `10 */12 * * * /bin/bash -c "hostname"`,
 			want:    1,
 		},
+		"just a job with seconds": {
+			content: `*/2 10 */12 * * * /bin/bash -c "hostname"`,
+			want:    1,
+		},
 		"all wild": {
 			content: `* * * * * /bin/bash -c "hostname"`,
 			want:    1,