Make beautons use variables

Fixes #165
Allow reversible grids

Fixes #166
[refs #169] Add default beautons colour.
Ensure beautons variables use `!default` flag.

Closes #165
[refs #182] Use new headings mixin courtesy of @thierrylemoulec
Merge branch 'fix/headings-mixin' into v5.1.1
Merge branch 'incoming' into v5.0.1
v5.0.1 updates
Make beautons use variables

Fixes #165
Ensure beautons variables use `!default` flag.

Closes #165

Conflicts:
	_defaults.scss
[refs #169] Add default beautons colour.

Conflicts:
	_defaults.scss
Allow reversible grids

Fixes #166
Merge branch 'fix/beautons' into v5.1.0

Conflicts:
	_defaults.scss
Merge branch 'fix/grids' into v5.1.0
Merge tag 'v5.0.1' into v5.1.0
Port over new csswizardry-grids features
Merge branch 'feature/grids' into v5.1.0
Add retina MQ. Closes #152
Merge branch 'feature/retina' into v5.1.0
Fix missing $class-type

Cannot compile `v5.1.0` branch due to missing `$class-type` variable. Removed reference and replace with `.`.