R1:d9af48cc52aa

Add language specification to code blocks

Summary: Add the language specification to code blocks in documentation.

Test Plan: Eyeball it.

Reviewers: chad, #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D13277