Add retrieve-neat-setting function

`retrieve-neat-setting` takes the default map `$_neat-grid-default` and merges
it with the map passed in to it (typically `$neat-grid`) and then retrieves the
value for the key passed into it.

core/_neat.scss

@@ -6,6 +6,8 @@
 
 @import "neat/settings/settings";
 
+@import "neat/functions/retrieve-neat-settings";
+
 @import "neat/mixins/grid-column";
 @import "neat/mixins/grid-container";
 @import "neat/mixins/grid-push";

core/neat/functions/_retrieve-neat-settings.scss

@@ -0,0 +1,18 @@
+@charset "UTF-8";
+/// Return a Neat setting.
+///
+/// @argument {map} $grid
+///
+/// @argument {string} $setting
+///
+/// @return {boolean | color | list | number | string}
+///
+/// @example scss
+///   _retrieve-neat-setting($neat-grid, columns)
+///
+/// @access private
+
+@function _retrieve-neat-setting($grid, $setting) {
+  $_grid-settings: map-merge($_neat-grid-defaults, $grid);
+  @return map-get($_grid-settings, $setting);
+}

core/neat/mixins/_grid-column.scss

@@ -3,7 +3,7 @@
 ///
 /// @argument {number (unitless)} $columns [1]
 ///
-/// @argument {map} $grid [$neat-default-grid]
+/// @argument {map} $grid [$neat-grid]
 ///   The grid used to generate the column.
 ///
 /// @example scss
@@ -18,9 +18,9 @@
 ///     margin-left: 20px;
 ///   }
 
-@mixin grid-column($columns: 1, $grid: $neat-default-grid) {
-  $_grid-columns: map-get($grid, columns);
-  $_grid-gutter: map-get($grid, gutter);
+@mixin grid-column($columns: 1, $grid: $neat-grid) {
+  $_grid-columns: _retrieve-neat-setting($grid, columns);
+  $_grid-gutter: _retrieve-neat-setting($grid, gutter);
 
   $_column-ratio: $columns / $_grid-columns;
 

core/neat/mixins/_grid-container.scss

@@ -1,7 +1,7 @@
 @charset "UTF-8";
 /// Creates a Neat grid container with clearfix.
 ///
-/// @argument {map} $grid [$neat-default-grid]
+/// @argument {map} $grid [$neat-grid]
 ///   The type of grid for this column.
 ///
 /// @example scss
@@ -16,7 +16,7 @@
 ///     display: block;
 ///   }
 
-@mixin grid-container($grid: $neat-default-grid) {
+@mixin grid-container($grid: $neat-grid) {
   &::after {
     clear: both;
     content: "";

core/neat/mixins/_grid-push.scss

@@ -1,11 +1,11 @@
 @charset "UTF-8";
 /// Push or pull a Neat grid column.
 ///
-/// @argument {number (unitless)} $push [false]
+/// @argument {number (unitless)} $_push [false]
 ///
-/// @argument {map} $grid [$neat-default-grid]
+/// @argument {map} $_grid [$neat-grid]
 ///   The grid to be used to generate the column. By default, the global
-///   `$neat-default-grid` will be used.
+///   `$neat-grid` will be used.
 ///
 /// @example scss
 ///   .element {
@@ -17,14 +17,14 @@
 ///     margin-left: calc((100% - (260px)) * 0.25 + 80px);
 ///   }
 
-@mixin grid-push($push: false, $grid: $neat-default-grid) {
-  $_grid-columns: map-get($grid, columns);
-  $_grid-gutter: map-get($grid, gutter);
+@mixin grid-push($_push: false, $_grid: $neat-grid) {
+  $_grid-columns: _retrieve-neat-setting($_grid, columns);
+  $_grid-gutter: _retrieve-neat-setting($_grid, gutter);
 
-  @if $push {
-    $_push-column-ratio: $push / $_grid-columns;
+  @if $_push {
+    $_push-column-ratio: $_push / $_grid-columns;
     $_total-gutters: ($_grid-columns + 1) * $_grid-gutter;
-    $_gutter-affordance: $_grid-gutter * ($push + 1);
+    $_gutter-affordance: $_grid-gutter * ($_push + 1);
     $_total-columns: "(100% - #{$_total-gutters})";
     $_margin-value: calc(#{unquote($_total-columns)} * #{$_push-column-ratio} + #{$_gutter-affordance});
 

core/neat/settings/_settings.scss

@@ -11,7 +11,19 @@
 ///
 /// @access private
 
-$neat-default-grid: (
+$_neat-grid-defaults: (
   columns: 12,
   gutter: 20px
 );
+
+/// User overrides of Bourbon configuration settings.
+///
+/// @type map
+///
+/// @property {number (unitless)} columns [12]
+///   Number of grid columns.
+///
+/// @property {number (with unit)} gutter [20px]
+///   Grid gutter width.
+
+$neat-grid: () !default;