adding new --output replacements. Thanks @danut007ro (closes #442)

README.md

@@ -42,9 +42,10 @@ which means you can modify it, redistribute it or use it however you like.
                              title, %(uploader)s for the uploader name,
                              %(autonumber)s to get an automatically incremented
                              number, %(ext)s for the filename extension,
-                             %(upload_date)s for the upload date (YYYYMMDD), and
-                             %% for a literal percent. Use - to output to
-                             stdout.
+                             %(upload_date)s for the upload date (YYYYMMDD),
+                             %(provider)s for the provider (youtube, metacafe,
+                             etc), %(id)s for the video id and %% for a literal
+                             percent. Use - to output to stdout.
     -a, --batch-file FILE    file containing URLs to download ('-' for stdin)
     -w, --no-overwrites      do not overwrite files
     -c, --continue           resume partially downloaded files