Add cross-browser support for video and audio files

[komollo]

If the author isn't adding video, then the application will work in most browsers. Due to HTML5 limitations, each browser only supports certain types of video and audio formats (https://developer.mozilla.org/en-US/docs/Media_formats_supported_by_the_audio_and_video_elements). Since this version doesn't do any auto-conversion of files, we recommend that it be used with Chrome. This is noted on the intro page.