[fix] bing unicode issue part III.

searx/engines/bing.py

     offset = (params['pageno'] - 1) * 10 + 1
 
     if params['language'] != 'all':
-        query = u'language:{} {}'.format(params['language'].split('_')[0].upper(), query.decode('utf-8'))
+        query = u'language:{} {}'.format(params['language'].split('_')[0].upper(), query.decode('utf-8')).encode('utf-8')
 
     search_path = search_string.format(
-        query=urlencode({'q': query.encode('utf-8')}),
+        query=urlencode({'q': query}),
         offset=offset)
 
     params['url'] = base_url + search_path