Adjusting live start time to 3 target durations

Changing the live start time from 30s to 3 target durations. Using 30s
as a fallback if the playlist does not define a target duration.

@@ -91,9 +91,10 @@ videojs.Hls.prototype.src = function(src) {
 
 videojs.Hls.setMediaIndexForLive = function(selectedPlaylist) {
   var tailIterator = selectedPlaylist.segments.length,
-      tailDuration = 0;
+      tailDuration = 0,
+      targetTail = (selectedPlaylist.targetDuration || 10) * 3;
 
-  while (tailDuration < 30 && tailIterator > 0) {
+  while (tailDuration < targetTail && tailIterator > 0) {
     tailDuration += selectedPlaylist.segments[tailIterator - 1].duration;
     tailIterator--;
   }

@@ -39,5 +39,5 @@
       "uri": "009.ts"
     }
   ],
-  "targetDuration": 19
+  "targetDuration": 10
 }
\ No newline at end of file

 #EXTM3U
 #EXT-X-MEDIA-SEQUENCE:0
 #EXT-X-ALLOW-CACHE:YES
-#EXT-X-TARGETDURATION:19
+#EXT-X-TARGETDURATION:10
 #EXTINF:10,0
 001.ts
 #EXTINF:19,0