[traileraddict] Obtain hd quality stream if available

No clear method for determining if hd is available so opted to just
check for presence of hd toggle function.

youtube_dl/extractor/traileraddict.py

@@ -19,22 +19,28 @@ class TrailerAddictIE(InfoExtractor):
         mobj = re.match(self._VALID_URL, url)
         video_id = mobj.group(1)
         webpage = self._download_webpage(url, video_id)
-        
+
         title = self._search_regex(r'<title>(.+?)</title>',
                 webpage, 'video title').replace(' - Trailer Addict','')
         view_count = self._search_regex(r'Views: (.+?)<br />',
                 webpage, 'Views Count')
         video_id = self._og_search_property('video', webpage, 'Video id').split('=')[1]
 
-        info_url = "http://www.traileraddict.com/fvar.php?tid=%s" %(str(video_id))
+        # Presence of (no)watchplus function indicates HD quality is available
+        if re.search(r'function (no)?watchplus()', webpage):
+            fvar = "fvarhd"
+        else:
+            fvar = "fvar"
+
+        info_url = "http://www.traileraddict.com/%s.php?tid=%s" % (fvar, str(video_id))
         info_webpage = self._download_webpage(info_url, video_id , "Downloading the info webpage")
-        
+
         final_url = self._search_regex(r'&fileurl=(.+)',
                 info_webpage, 'Download url').replace('%3F','?')
         thumbnail_url = self._search_regex(r'&image=(.+?)&',
                 info_webpage, 'thumbnail url')
         ext = final_url.split('.')[-1].split('?')[0]
-        
+
         return [{
             'id'          : video_id,
             'url'         : final_url,