vimeo: Also accept URLs prefixed by www.

I hope that this doesn't break anything. `:)`

diff --git a/youtube-dl b/youtube-dl
index a925c9783663c03e77301cf34c9d40cdd9212207..16d234ebf0af717f63dcd0f741419c16c3aed3be 100755 (executable)
--- a/youtube-dl
+++ b/youtube-dl
@@ -1723,7 +1723,7 @@ class VimeoIE(InfoExtractor):
        """Information extractor for vimeo.com."""
 
        # _VALID_URL matches Vimeo URLs
-       _VALID_URL = r'(?:http://)?vimeo\.com/([0-9]+)'
+       _VALID_URL = r'(?:http://)?(?:www.)?vimeo\.com/([0-9]+)'
 
        def __init__(self, downloader=None):
                InfoExtractor.__init__(self, downloader)