Merging in scss .ss-fw fix from @pioz

fix scss version of .ss-fw class (issue #67)

sass/_helpers.scss

@@ -8,6 +8,13 @@
   }
 }
 
+/** Set Symbol Fix Width =========================
+ */
+.#{$keyrune_prefix}-fw {
+  width: calc(18em / #{$keyrune_font_size / ($keyrune_font_size * 0 + 1)});
+  text-align: center;
+}
+
 /** Set Symbol No Border =========================
  * | This class can remain a singleton since it is generic, making
  * | it a helper class.

sass/_variables.scss

@@ -40,8 +40,7 @@ $keyrune_sizes: (
   '3x': 3em,
   '4x': 4em,
   '5x': 5em,
-  '6x': 6em,
-  'fw': calc(18em / #{$keyrune_font_size})
+  '6x': 6em
 ) !default;
 
 // NOTE: not really sure what to call this array. I notice it is for special borders of sorts, so setlist_borders it is.