Stop hard-coding the video file extension.

README.md

@@ -29,7 +29,6 @@ premium subscription!**
 
 ### Pending Implementation
 
-* Detect and write the appropriate video extension (instead of hard-code mp4).
 * Add ASS support.
 * Add muxing (MP4+ASS=MKV).
 * Add series API to download an entire series rather than per-episode.

src/episode.js

@@ -132,6 +132,6 @@ function _video(config, page, player, filePath, done) {
     player.video.host,
     player.video.file,
     page.swf,
-    filePath + '.mp4',
+    filePath + '.' + path.extname(player.video.file),
     done);
 }