fix timeformat in angular example (katspaugh#1448)

Change the time format for seconds from ceil to floor so it shows 01:00 instead of 00:00

example/angular-material/wavesurfer.directive.js

@@ -101,7 +101,7 @@
             }
 
             var minutes = Math.floor(input / 60);
-            var seconds = Math.ceil(input) % 60;
+            var seconds = Math.floor(input) % 60;
 
             return (
                 (minutes < 10 ? '0' : '') +