Update CHANGELOG notes to version 3.1.3

Merge branch 'feature/artokai-patch-1' into develop

Merge branch 'patch-1' of https://github.com/artokai/minimal-mistakes into feature/artokai-patch-1

Fix SEO author bug
- If `twitter.username` is set and `author.twitter` is nil bad things happen.
- Close #289

Allow `author_profile` to be toggled in a _layout (eg. archive-taxonomy.html)
- Close #285

Remove white space as it was causing issues with Markdown and parsing as code blocks
- Close #279

Fix "build:all" npm script

The script "build:all" was missing the "npm run" section for the "build:js" part.

Fix site.og_image URL by appending /images/ the path
- Close #277

Update README

Merge branch 'release/3.1.2' into develop

Update CHANGELOG

Improve nav_list helper to be used with any type of navigation list defined in navigation.yml data file
- Close #272

Merge branch 'feature/related-posts-alignment' into develop

Decrease left/right page padding on small screens to give more space for content.

Fix related posts alignment
- Close #273

Fix alignment of "Follow" button in author profile
- Close #274

Merge branch 'hotfix/3.1.1' into develop

Update CHANGELOG

Fix reading time bug
- Close #271

Merge branch 'release/3.1.0'

Conflicts:
	CHANGELOG.md