Permit choice of dash to separate words in page and post names.

A word_sep keyword argument is added to several functions and is
ultimately used in utils.name_from_title(). I also ensure that only
one instance of the word sep char appears between words and that
there are no leading or trailing non-word chars in the name. I'd
like to propose the same for other page/post/draft creation options.

I just found Tinkerer yesterday and it seems to be exactly what I've
been looking for in a blogging tool!
Add word_sep option to drafts and pages.
Return feed rss.xml, not .html.
Oof, changing the feed from rss.html and rss.xml is more difficult
than it seemed. Reverting.
Merge pull request #26 from sgillies/master

Permit choice of dash to separate words in page and post names.