[cnn] Use edition.cnn.com for getting the information (fixes #4757)

Some videos (like http://edition.cnn.com/videos/us/2015/01/20/orig-yellowstone-oil-spill.cnn) will fail if we use cnn.com.

youtube_dl/extractor/cnn.py

@@ -51,7 +51,7 @@ class CNNIE(InfoExtractor):
         mobj = re.match(self._VALID_URL, url)
         path = mobj.group('path')
         page_title = mobj.group('title')
-        info_url = 'http://cnn.com/video/data/3.0/%s/index.xml' % path
+        info_url = 'http://edition.cnn.com/video/data/3.0/%s/index.xml' % path
         info = self._download_xml(info_url, page_title)
 
         formats = []