Variabilise dark gray used by icon controls

Signed-off-by: Alex Coles <alex@alexbcoles.com>

app/assets/stylesheets/_settings.scss

@@ -103,7 +103,7 @@ $include-css: (
 // $warning-color: #F08A24;
 // $dark-color: #232323;
 $gray: #EAEAEA;
-$gray-dark: darken($gray, 8);
+$gray-dark: #878787;
 $gray-light: #F8F8F8;
 
 // We use these to make sure border radius matches unless we want it different.

app/assets/stylesheets/content/_icon_control.sass

@@ -36,7 +36,7 @@
   text-align:     center
   cursor:         pointer
   border-radius:  50%
-  color:          #878787
+  color:          $gray-dark
 
   &:hover, &.-active
     text-decoration:  none
@@ -44,7 +44,7 @@
     background:       $button-highlight-background-gradient
 
   &.-active:hover
-    color:            #878787
+    color:            $gray-dark
     background:       white
 
 .icon-control--icon