PEP 12: Update spacing/breaking conventions to match current practice

[CAM-Gerlach]

As proposed by @JelleZijlstra in this comment and widely agreed on there.

[JelleZijlstra]

Thanks!

I might also want to drop the Emacs stanza but I have no real idea what it does.

[warsaw]

I might also want to drop the Emacs stanza but I have no real idea what it does.

It sets up some file-specific settings in Emacs's indented-text mode, like the column to fill paragraphs in (70), to use two spaces at the end of sentences, and to use UTF-8 encoding. These were helpful way back in the day, but they are probably safe to get rid of. Us 3 Emacs users still out there can just use rst-mode now.

[CAM-Gerlach]

I thought about that, but for obvious reasons I didn't want to be too bold here. But it makes good sense from your comments, since those are the same required settings that are no longer required here, and its one more chunk of boilerplate that future PEP authors needn't worry about any more (and of course, PEP authors can still add it to their PEPs, should they themselves need it—that's who it's for, after all). In any case, I've implemented it as requested.