Adjust minimum and maximum levels to allow all headings and fix CSS to style indentation and nested lists properly in jekyll-toc and Kramdown generated table of contents.
Fixes#1782
* 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 `$muted-text-color`
* Add `contrast` and `sunrise` skin colors
* Add `dirt` skin color
* Add `air` skin color option
* Add `mint` skin color
* Add `btn--primary` class to Submit Comment button
* Set skin to `default`
* Document skin color options
* Add note about skin SCSS import
Close#1208
* Fix collapsed white-space above pagination links
* Improve `page` and `archive` layout
- Center main content on page
- Harmonize sidebar columns to be equal widths
Fixes#1155
* Update CHANGELOG and history
* Position and align right sidebar with the top of the main content
* Offset right sidebar at `$large` viewport
* Add TOC bottom include test post
* Add right sidebar styling edits to documentation site
* Add TOC bottom include test post
Most of Susy's mixins have been deprecated, `@include container()`, `@include full()`, `@include span()`, `@include prefix()`, `@include suffix()`, `@include gallery()`, etc.
Fixes#1114
