FIX: add more consistent gutter to ace editor

old css hack had issues when line number was higher than 10

app/assets/javascripts/admin/components/ace-editor.js.es6

@@ -63,6 +63,7 @@ export default Ember.Component.extend({
           this._skipContentChangeEvent = false;
         });
         editor.$blockScrolling = Infinity;
+        editor.renderer.setScrollMargin(10,10);
 
         this.$().data('editor', editor);
         this._editor = editor;

app/assets/javascripts/admin/templates/customize-themes-edit.hbs

@@ -41,7 +41,6 @@
     </div>
 
     <div>
-      <div class='custom-ace-gutter'></div>
       {{ace-editor content=activeSection editorId=editorId mode=activeSectionMode autofocus="true"}}
     </div>
 

app/assets/stylesheets/common/admin/customize.scss

@@ -99,12 +99,6 @@
       }
     }
 
-    .custom-ace-gutter {
-      width: 41px;
-      background-color: #ebebeb;
-      height: 15px;
-    }
-
     .ace_editor {
       position: absolute;
       left: 0;