* Add YIQ Color Contrast mixin
* Remove text underline from `.btn` links
* Move YIQ variables
* Simplify button classes using YIQ color contrast mixin
- DRY up button CSS using Sass list and YIQ color contrast mixin.
- Move `color` and `background-color` to new `btn--primary` class instead of assinging on the default class. Removes the need to override them.
* Add `.btn--primary` to buttons that just had `.btn`
* Apply changes to `/docs`
* Add `.btn--primary` class
* Update CHANGELOG and history
* Add sample form
* Abstract colors away into Sass variables for easier themeing
* Add "dark" skin
* Replace hardcoded color with SCSS variable
* Invert Font Awesome icons' colors in author sidebar and footer
* Add Sass changes to `/docs`
* Use primary button type instead of inverse
* Add missing `!default` on `$muted-text-color`
* Add `contrast` and `sunrise` skin colors
* Add `dirt` skin color
* Add `air` skin color option
* Add `mint` skin color
* Add `btn--primary` class to Submit Comment button
* Set skin to `default`
* Document skin color options
* Add note about skin SCSS import
Close#1208
`site.related_posts` should return an array of latest posts when no related ones are found due to `lsi` being disabled (GitHub Page's doesn't support it).
This works around that bug by showing the 4 latest posts to populate the "You May Also Enjoy" module when enabled with `related: true`.
Fixes#554
Related: #978#1022
Liquid does not allow parenthesis, remove them to fix Liquid Exception: Liquid syntax error "Expected dotdot but found pipe" in `tag-list.html` and `category-list.html`
Close#1223
Correct "Posts by Tag" (singular) to be more consistent with "Posts by Category"
* Update tag-archive.html
* Update about.md
* Update 10-layouts.md
* Update README.md
* Update 14-helpers.md
