Merge branch 'release/4.0.4'

Conflicts:
	README.md

Merge branch 'feature/theme-gem' into develop

Replace base_path with `absolute_url` filter where possible

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

Merge branch 'release/3.3.5'

Add `en` default text to `site.locale` strings
- Close #407

Merge branch 'release/3.0.0'

Merge branch 'feature/documentation-and-demo' into develop

Make base_path available to all includes that need it

Add LinkedIn social share button and add ARIA hidden to Font Awesome icons
- Close #174
- Close #179

Merge branch 'feature/visual-refresh' into develop

More style cleanup and housekeeping

Edit sidebar and page meta styles

Add file extensions back to non-helper _includes

Cleanup SCSS

Remove locale hash to shorten Liquid variable names

Add support for localizing UI text with a _data file

Merge branch 'feature/refactor-includes-layouts' into develop

Merge branch 'feature/refactor-layouts' into develop