Update position add on to utilize false/null rather than unitless zer…

…o values.

app/assets/stylesheets/addons/_position.scss

@@ -1,4 +1,4 @@
-@mixin position ($position: relative, $coordinates: 0 0 0 0) {
+@mixin position ($position: relative, $coordinates: null null null null) {
 
   @if type-of($position) == list {
     $coordinates: $position;
@@ -14,19 +14,19 @@
 
   position: $position;
 
-  @if ($top and $top == auto) or (type-of($top) == number and not unitless($top)) {
+  @if ($top and $top == auto) or (type-of($top) == number) {
     top: $top;
   }
 
-  @if ($right and $right == auto) or (type-of($right) == number and not unitless($right)) {
+  @if ($right and $right == auto) or (type-of($right) == number) {
     right: $right;
   }
 
-  @if ($bottom and $bottom == auto) or (type-of($bottom) == number and not unitless($bottom)) {
+  @if ($bottom and $bottom == auto) or (type-of($bottom) == number) {
     bottom: $bottom;
   }
 
-  @if ($left and $left == auto) or (type-of($left) == number and not unitless($left)) {
+  @if ($left and $left == auto) or (type-of($left) == number) {
     left: $left;
   }
 }