Update gems

Merge branch 'release/3.1.8' into develop

Update CHANGELOG

Remove duplicate fa-twitter and fa-twitter-square classes from _utilities.scss
- Fixes #302

Make page.title conditional in <h1>
- Fix #312

Merge branch 'release/3.1.7' into develop

Update CHANGELOG

Merge branch 'feature/translate-recent-posts-title' into develop

Merge branch 'master' of https://github.com/flohw/minimal-mistakes into feature/translate-recent-posts-title

Merge branch 'feature/underline-fix' into develop

Merge branch 'fix-ws' of https://github.com/tobie/minimal-mistakes into feature/underline-fix

Translate index page title

Merge branch 'release/3.1.6' into develop

Merge branch 'release/3.1.6'

Bump version to 3.1.6

Update dependencies

Fix whitespace issue using CSS.

Merge branch 'release/3.1.5' into develop

Merge branch 'release/3.1.5'

Update CHANGELOG for 3.1.5