More doc bugs: unified_diff and context_diff say 'lists of strings' when 'sequences of strings' is correct. Docstrings do say 'sequences'.

In 3.x, SequenceMatcher.get_matching_blocks return a map objects rather than a list. In spite of my original post, the items are tuples in 3.3, as least in one test. Named tuples in 3.4 would be good. I might call it an iterable of (names) triples instead of 'map object' as that is more relevant for the user. I think I should check all arg and return types in code, docstring, and doc for consistency and separately check on and as necessary upgrade namedtuple usage.