Reorganize test vectors

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=133935070

demo/src/main/java/com/google/android/exoplayer2/demo/SampleChooserActivity.java

@@ -65,6 +65,7 @@ public class SampleChooserActivity extends Activity {
     } else {
       uris = new String[] {
           "asset:///media.exolist.json",
+          "https://raw.githubusercontent.com/Axinom/dash-test-vectors/master/axinom.exolist.json",
       };
     }
     SampleListLoader loaderTask = new SampleListLoader();