OpenGraph support
Notes: you need description filed defined in your article files to fill "og:description" tag in article.
Merge pull request #32 from paskal/master

Fix for article.html description itemprop
Merge pull request #33 from paskal/OpenGraph

OpenGraph support
use the null layout to avoid warning while `rake generate'
Display the post date, fix #34 and fix #36
Merge remote-tracking branch 'upstream/master'

Conflicts:
	source/_includes/post/date.html