refactor: add "default" position to grid-column-positioning to hand…

…le float position

Handle all the float positioning of Float Grid in the same mixin. This also makes the "last column" selector used only in this mixin.

scss/grid/_column.scss

@@ -63,12 +63,8 @@
   // Gutters
   @include grid-column-gutter($gutters: $gutters);
 
-  // Last column alignment
-  @if $grid-column-align-edge {
-    &:last-child:not(:first-child) {
-      float: $global-right;
-    }
-  }
+  // Position
+  @include grid-col-pos(auto);
 }
 
 /// Creates a grid column row. This is the equivalent of adding `.row` and `.column` to the same element.

scss/grid/_position.scss

@@ -8,14 +8,35 @@
 
 /// Reposition a column.
 ///
-/// @param {Number|Keyword} $position - Direction and amount to move. The column will move equal to the width of the column count specified. A positive number will push the column to the right, while a negative number will pull it to the left. Set to center to center the column.
+/// @param {Number|Keyword} $position - It can be:
+///   * A number: The column will move equal to the width of the column count
+///     specified. A positive number will push the column to the right, while
+///     a negative number will pull it to the left.
+///   * `center`: Column will be centered
+///   * `auto`: Column will be pushed to the left (or to the right for the last column).
 @mixin grid-column-position($position) {
-  @if type-of($position) == 'number' {
+  // Auto positioning
+  @if $position == auto {
+    float: $global-left;
+    clear: none;
+
+    // Last column alignment
+    @if $grid-column-align-edge {
+      &:last-child:not(:first-child) {
+        float: $global-right;
+      }
+    }
+  }
+
+  // Push/pull
+  @else if type-of($position) == 'number' {
     $offset: percentage($position / $grid-column-count);
 
     position: relative;
     #{$global-left}: $offset;
   }
+
+  // Center positioning
   @else if $position == center {
     &, &:last-child:not(:first-child) {
       float: none;
@@ -24,23 +45,18 @@
     margin-right: auto;
     margin-left: auto;
   }
+
   @else {
-    @warn 'Wrong syntax for grid-column-position(). Enter a positive or negative number, or center.';
+    @warn 'Wrong syntax for grid-column-position(). Enter a positive or negative number, "center" or "auto".';
   }
 }
 
 /// Reset a position definition.
 @mixin grid-column-unposition {
+  @include grid-column-position(auto);
   position: static;
   margin-right: 0;
   margin-left: 0;
-
-  float: $global-left;
-  @if $grid-column-align-edge {
-    &:last-child:not(:first-child) {
-      float: $global-right;
-    }
-  }
 }
 
 /// Offsets a column to the right by `$n` columns.