Create vendor sass function

Author: Aaron Imming

src/assets/sass/base/mixins.scss

@@ -0,0 +1,7 @@
+@mixin vendor($property, $value) {
+    $prefixes: ('moz', 'webkit', 'ms', 'o');
+    @each $prefix in $prefixes {
+        -#{$prefix}-#{$property}: #{$value};
+    }
+    #{$property}: #{$value};
+}