remove duplicate 'if cr == (0, 0):' in get_terminal_size
Merge pull request #1941 from mekarpeles/I1939/hotfix/duplicate-code

remove duplicate 'if cr == (0, 0):' in get_terminal_size
minor fixes to changelog
Raise NotImplementedError (not NotImplemented)

NotImplemented is a singleton intended for use in __eq__ methods where comparison is not possible for some reason.
Merge pull request #1947 from mjg123/patch-1

Raise NotImplementedError (not NotImplemented)