renaming -selector variable to and moving the option before as sugges…

…ted in #171 (comment)

docs/source/guides/reference.html.md

@@ -356,18 +356,18 @@ Provide the column-width of each element,
 and Susy will determine the positioning for you.
 
     :::scss
-    // isolate-grid(<$columns> [, <$context>, <$from>, <$nth-selector>, <$style>])
+    // isolate-grid(<$columns> [, <$context>, <$selector>, <$from>, <$style>])
     .gallery-item {
       @include isolate-grid(3);
     }
 
 - `<$columns>`: The number of _Columns_ for each item to span.
 - `<$context>`: Current nesting _Context_.
   Default: `$total-columns`.
+- `<$selector>`: either 'child' or 'of-type'.
+  Default: `child`.
 - `<$from>`: The origin direction of your document flow.
   Default: `$from-direction`.
-- `<$nth-selector>`: either 'child' or 'of-type'.
-  Default: `child`.
 - `<$style>`: Optionally return `static` lengths for grid calculations.
   Default: `$container-style`.
 

sass/susy/_isolation.scss

@@ -21,13 +21,13 @@
 //
 // $columns       : The column-width of each item on the grid;
 // $context       : [optional] The context (columns spanned by parent).
+// $selector      : [child | of-type | last-of-type ] (default is 'child')
 // $from          : The start direction of your layout (e.g. 'left' for ltr languages)
-// $nth-selector  : [optional] change between 'child' or 'of-type' (default is 'child')
 @mixin isolate-grid(
   $columns,
   $context: $total-columns,
+  $selector: 'child',
   $from: $from-direction,
-  $nth-selector: 'child',
   $style: fix-static-misalignment()
 ) {
   $to: opposite-position($from);
@@ -39,7 +39,7 @@
 
   @for $item from 1 through $line {
     $nth: '#{$line}n + #{$item}';
-    &:nth-#{$nth-selector}(#{$nth}) {
+    &:#{format-nth($nth,$selector)} {
       margin-#{$from}: space($location - 1, $context, $style);
       @if $location == 1 { clear: $from; }