Enable @mention for posts?

[RaoOfPhysics]

https://help.github.com/articles/mentions-on-github-pages/

┆Issue is synchronized with this Asana task

[RaoOfPhysics]

Not really needed, since we're linking through to author Twitter accounts, instead of GitHub ones.

[neuroamanda]

link through to author archive instead?

[RaoOfPhysics]

Hmm. Not sure how author archives work in Jekyll, but perhaps I can tie it with categories (#19).