Correct a bug in firefox regarding seeking before play

Firefox doesn't allow you to seek until 'canplay' is fired and doesn't fire canplay until after playback has begun. As a result, seeking to the right point in a live stream requires setupFirstPlay to wait for 'canplay' and check that the readyState signifies that we can finally seek.

@@ -165,6 +165,8 @@ videojs.HlsHandler.prototype.src = function(src) {
   }
   this.playlists = new videojs.Hls.PlaylistLoader(this.source_.src, this.options_.withCredentials);
 
+  this.tech_.on('canplay', this.setupFirstPlay.bind(this));
+
   this.playlists.on('loadedmetadata', function() {
     oldMediaPlaylist = this.playlists.media();
 
@@ -422,7 +424,11 @@ videojs.HlsHandler.prototype.setupFirstPlay = function() {
       this.sourceBuffer &&
 
       // 4) the active media playlist is available
-      media) {
+      media &&
+
+      // 5) the video element or flash player is in a readyState of
+      // at least HAVE_FUTURE_DATA
+      this.tech_.readyState >= 3) {
 
     // seek to the latest media position for live videos
     seekable = this.seekable();
@@ -1138,7 +1144,6 @@ videojs.HlsHandler.prototype.drainBuffer = function() {
   segment = playlist.segments[mediaIndex];
 
   if (segment.key && !bytes) {
-
     // this is an encrypted segment
     // if the key download failed, we want to skip this segment
     // but if the key hasn't downloaded yet, we want to try again later