Merge branch 'release/4.0.4'

Conflicts:
	README.md

Merge branch 'feature/theme-gem' into develop

Remove `prepend: "/"` from includes and add to image path's instead

Make author avatar optional

Replace base_path with `absolute_url` filter where possible

Update seo.html for meta description (#558)

Adding standard meta description immediately after seo_description has been defined

Don't prepend `author.avatar` paths with `/` when path contains `://`

Allow images to be placed in other folders
- Remove `images/` only restriction and encourage placement in `assets/images/` instead

Merge branch 'release/3.4.8'

includes: Enhance Twitter share link (#538)

* Include the page title before the URL
* If twitter.username is set, pass the `via` paramter for attribution

Fixed Last.fm URL (#540)

lastfm.com/user... results in a server error, last.fm/user... is the correct URL.

Merge branch 'release/3.4.7'

Remove duplicate include of base_path in category-list.html (#522)

Merge branch 'release/3.4.5'

get Follow-Button label from ui-text and default to "Follow" (#496)

Merge branch 'release/3.4.3'

Add structured data markup for `itemprop="comment"`
- Close #458

Use page.header.teaser instead of site.og_image in twitter:image and og:image meta tags (#466)

Merge branch 'develop' of https://github.com/mmistakes/minimal-mistakes into develop

* 'develop' of https://github.com/mmistakes/minimal-mistakes:
  formats og:locale tag with underscores (#465)

formats og:locale tag with underscores (#465)

See http://fbdevwiki.com/wiki/Locales