(py-mode): comment-start is now "# " so indent-for-comment does the right thing.
(py-mode): comment-start is now "# " so indent-for-comment does the
right thing.

(py-comment-region): let-bind comment-start to "## " so commented
regions get transformed into non-indenting comment lines.

(py-compute-region): Implement modification to rule for recognizing
"indenting comment lines".

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