[vimeo] Fix m3u8 formats

Reported at
https://github.com/rg3/youtube-dl/pull/7126#issuecomment-147327584

youtube_dl/extractor/vimeo.py

@@ -406,7 +406,7 @@ class VimeoIE(VimeoBaseInfoExtractor):
             m3u8_formats = self._extract_m3u8_formats(
                 m3u8_url, video_id, 'mp4', 'm3u8_native', 0, 'hls', fatal=False)
             if m3u8_formats:
-                formats.append(m3u8_formats)
+                formats.extend(m3u8_formats)
         for key in ('other', 'sd', 'hd'):
             formats += files[key]
         self._sort_formats(formats)