Require typed arrays for the tech to be supported

Typed arrays are used extensively in repackaging segments. Make sure the tech doesn't load on platforms they're not available on (e.g. IE8). Fixes #137.

@@ -513,9 +513,15 @@ videojs.Hls.supportsNativeHls = (function() {
 })();
 
 videojs.Hls.isSupported = function() {
+
+  // Only use the HLS tech if native HLS isn't available
   return !videojs.Hls.supportsNativeHls &&
+    // Flash must be supported for the fallback to work
     videojs.Flash.isSupported() &&
-    videojs.MediaSource;
+    // Media sources must be available to stream bytes to Flash
+    videojs.MediaSource &&
+    // Typed arrays are used to repackage the segments
+    window.Uint8Array;
 };
 
 videojs.Hls.canPlaySource = function(srcObj) {

@@ -1152,6 +1152,15 @@ test('has no effect if native HLS is available', function() {
   player.dispose();
 });
 
+test('is not supported on browsers without typed arrays', function() {
+  var oldArray = window.Uint8Array;
+  delete window.Uint8Array;
+  ok(!videojs.Hls.isSupported(), 'HLS is not supported');
+
+  // cleanup
+  window.Uint8Array = oldArray;
+});
+
 test('tracks the bytes downloaded', function() {
   player.src({
     src: 'http://example.com/media.m3u8',