Merge remote-tracking branch 'jaimemf/format_spec_groups' (closes #6124)

diff --cc README.md
Simple merge

diff --cc youtube_dl/YoutubeDL.py
Simple merge

diff --cc youtube_dl/compat.py
index e4b9286c06e12d967f60b5fbcf2c691802684163,bc218dd719074204b3e94e7ec124f02914b28f51..ace5bd716aac0161b356625260f1138687568314
--- 1/youtube_dl/compat.py
--- 2/youtube_dl/compat.py
+++ b/youtube_dl/compat.py
@@@ -426,16 -388,11 +426,21 @@@ else
              pass
          return _terminal_size(columns, lines)
  
 +try:
 +    itertools.count(start=0, step=1)
 +    compat_itertools_count = itertools.count
 +except TypeError:  # Python 2.6
 +    def compat_itertools_count(start=0, step=1):
 +        n = start
 +        while True:
 +            yield n
 +            n += step
 +
+ if sys.version_info >= (3, 0):
+     from tokenize import tokenize as compat_tokenize_tokenize
+ else:
+     from tokenize import generate_tokens as compat_tokenize_tokenize
+ 
  __all__ = [
      'compat_HTTPError',
      'compat_basestring',