Correct docs for ABCs (MutableSequence was missing __setiem).  Simplify the table by taking out inherited requirements for abstract methods.
Correct docs for ABCs (MutableSequence was missing __setiem).  Simplify the table by taking out inherited requirements for abstract methods.

sk-/python2.7-type-annotator,sk-/python2.7-type-annotator,sk-/python2.7-type-annotator