Replace a single quote with double quote

docs/assets/css/docs.css

@@ -64,7 +64,7 @@ body {
   background-image:     -ms-linear-gradient(45deg, #0a1855 0%, #da0024 100%);
   background-image:      -o-linear-gradient(45deg, #0a1855 0%, #da0024 100%);
   background-image:         linear-gradient(45deg, #0a1855 0%, #da0024 100%);
-  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#0a1855', endColorstr='#da0024', GradientType=1);
+  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr="#0a1855", endColorstr="#da0024", GradientType=1);
 }
 
 .docs-header {

sass/mixins.scss

@@ -55,7 +55,7 @@
   background-image:     -ms-linear-gradient(45deg, $color-from 0%, $color-to 100%);           // IE10+
   background-image:      -o-linear-gradient(45deg, $color-from 0%, $color-to 100%);           // Opera 11.10+
   background-image:         linear-gradient(45deg, $color-from 0%, $color-to 100%);     // W3C
-  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#{$color-from}', endColorstr='#{$color-to}', GradientType=1); // IE6-9
+  filter: progid:DXImageTransform.Microsoft.gradient(startColorstr="#{$color-from}", endColorstr="#{$color-to}", GradientType=1); // IE6-9
 }