adds new mixin partial and includes updated strip-unit, em(), rem() a…

…nd new line height mixins for use with Bourbon 5 (#254)

assets/sass/utilities/mixins/_units-of-measure.scss

@@ -0,0 +1,69 @@
+//--------------------------------------------------------------
+// Size Conversion SCSS Mixins
+//--------------------------------------------------------------
+
+//-----------------------------------------
+// Strip Units Forked from Bourbon 4 https://github.com/thoughtbot/bourbon/blob/v4-stable/app/assets/stylesheets/functions/_strip-units.scss
+//-----------------------------------------
+@function strip-unit($number) {
+	@if type-of($number) == "number" and not unitless($number) {
+		@return $number / ($number * 0 + 1);
+	}
+
+	@return $number;
+}
+
+//-----------------------------------------
+// PX to EM Forked from Bourbon 4 https://github.com/thoughtbot/bourbon/blob/v4-stable/app/assets/stylesheets/functions/_px-to-em.scss
+// Usage em(12) — defaults context to 16
+// Usage em(12, 16) = same as above.
+//-----------------------------------------
+@function em($pixelvalue, $context: $base-context) {
+
+	@if not unitless($pixelvalue) {
+		$pixelvalue: strip-units($pixelvalue);
+	}
+
+	@if not unitless($context) {
+		$base: strip-units($context);
+	}
+
+	@return ($pixelvalue / $base-context) * 1em;
+}
+
+
+//-----------------------------------------
+// PX to REM Forked from Bourbon 4 https://github.com/thoughtbot/bourbon/blob/v4-stable/app/assets/stylesheets/functions/_px-to-rem.scss
+// Usage em(12) — defaults context to 16
+// Usage em(12, 16) = same as above.
+//-----------------------------------------
+@function rem($pixelvalue, $context: $base-context) {
+
+	@if not unitless($pixelvalue) {
+		$pixelvalue: strip-units($pixelvalue);
+	}
+
+	@if not unitless($context) {
+		$base: strip-units($context);
+	}
+
+	@return ($pixelvalue / $base-context) * 1rem;
+}
+
+//-----------------------------------------
+// Unitless Line Height
+// Usage lh(12) = lh(12,12) = 1
+// Usage lh(24, 12) = 2
+//-----------------------------------------
+@function lh($font-size, $line-height: $font-size) {
+
+	@if not unitless($font-size) {
+		$font-size: strip-units($font-size);
+	}
+
+	@if not unitless($line-height) {
+		$line-height: strip-units($line-height);
+	}
+
+	@return $font-size / $line-height;
+}

assets/sass/utilities/mixins/index.scss

@@ -5,7 +5,8 @@
 @import "margin-auto";
 @import "margin-padding-reset";
 @import "omega-reset";
-@import "word-break";
-@import "z-index";
 @import "reverse-list";
-@import "vertical-align";
+@import "units-of-measure";
+@import "vertical-align";
+@import "word-break";
+@import "z-index";