Look into updating with sass:string

[todo]

saturnfive/module/_spacing.scss

Lines 4 to 9 in 85cc732

	// TODO: Look into updating with sass:string
	@mixin padding($padding-location: 'shorthand top right bottom left', $size...) {
	@if $padding-location == number {
	@error '`#{$padding-location}` is not a valid value for $padding-location. Please set $padding-location to a string value. ';
	}

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This issue was generated by todo based on a TODO comment in 85cc732 when #80 was merged. cc @voyagerstudio.