Make the expand/collapse buttons bigger in the new sidebar

There is now a lot more padding around the bottom, left, and right sides of the expand/collapse buttons. This makes them a much easier hit-target than they were before.

Author: chasenlehara

static/sidebar.less

@@ -136,8 +136,9 @@ canjs-sidebar {
     border: 0;
     color: @link-color;
     cursor: pointer;
+    padding: @gutter/4 @gutter @gutter*2 @gutter*2;
     position: absolute;
-    right: 0;
+    right: 0 - @gutter;
     top: 0;
   }
 }