Social media integration

[codehag]

This is a nice to have: integrate well with social media. This means having support for twitter cards hcards and possibly a few others (though this should cover a lot)

I think, for generic posts we should have a SpiderMonkey image. For other posts, we can use the monkey posters as necessary? Jekyll has support for this: http://jekyll.github.io/jekyll-seo-tag/usage/