Extract common article info footer into an include

The article info footer (article date, "x minute read", and tags) occur in three places (article list, article view,
and articles-by-tag).

This commit deduplicates the redundant code from these three places into a single include.

Fix og images

Fix retina.js + truncate warning

Add better support for local fonts and update documentation (#60)

Put back styling on share icons

Add emoji support

Use new Jekyll relative_url and absolute_urls (#7)