Sharing buttons on blog posts

[preaction]

https://simplesharingbuttons.com

Add some sharing buttons to the bottom of blog posts on both the list view and the inner view. We already have font-awesome via CDN, so we can use the font-awesome version of the icons.

Questions:

• Should these buttons be opt-in or opt-out? We can add a share hash to the site's data attribute with keys to enable/disable buttons. Given that, I'd probably prefer it be opt-in, since explicitly opt-out with share: false or share: { twitter: false } is weird. But it's also a lot of work to opt-in, and people probably want this more than not.

[lindleyw]

A default to opt-out for newly generated sites (create config entry = true), and opt-in for existing ones (missing config entry) would be least surprising.

[preaction]

Okay. Kentnl on IRC agreed, and that sounds the most sane and in line with the philosophy we've had of not breaking existing sites (which is why we generally recommend bundling the theme, so your site is secure from theme changes).