(py-mode-map): Add a binding of C-m to py-newline-and-indent. This is

(py-mode-map): Add a binding of C-m to py-newline-and-indent.  This is
a religious issue: RMS decrees that the Enter (RET) key should just do
a newline and a LFD (C-j) should do a newline and indent (i.e. the
python-mode version of this).  Almost everyone I know disagrees and
finds that RET should do newline and indent.  Almost everyone hacks
their modes to do this, if they know how.  Because it's hard for
newbies to figure out how to do this, and because most DOS keyboards
lack a LFD (leaving users to the more obscure C-j), I think it makes
better sense to add this default binding.