Upgrade Sass from 3.1.20 to 3.2.7

The ability to pass content blocks to mixins was added in Sass 3.2,
which I will need for my next commit in which I add a `respond-to`
mixin.
Update to latest version of my Slash theme

The new version includes stripping of html from title tags, which will
be needed for my next commit, in which I introduce an HTML tag to my
post title.
Disable sharing bar on CSS post

These sharing bars usually seem like clutter and a waste of space, so
I'm disabling it.
Improve styling

I wanted to make the blog look a little nicer, so I played around with
tweaking some styles. Big changes include making the post title large,
getting rid of the left gutter (1 column layout), and making the first
paragraph extra large as a lead-in.