doc: style fixes for the TOC

- Hide the scrollbar on the TOC on all browsers. It was never the
  intention for it to be visible with the scroll indication in place.
  A wrapper element with 20px padding was added to accommodate for
  hopefully all scrollbar widths as well as to avoid overflowing
  content.
- Fixed the scroll indication gradient on Safari, which was caused by
  the wrong from-color, which now matches the to-color.
- Fixed a issue in old IE where the TOC didn't render on the correct
  position through setting `left: 0` and `top: 0` on it.

PR-URL: https://github.com/nodejs/node/pull/4748
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/template.html

@@ -11,12 +11,14 @@
 <body class="alt apidoc" id="api-section-__FILENAME__">
   <div id="content" class="clearfix">
     <div id="column2" class="interior">
-      <div id="intro" class="interior">
-        <a href="/" title="Go back to the home page">
-          Node.js (1)
-        </a>
+      <div class="no-scrollbar">
+        <div id="intro" class="interior">
+          <a href="/" title="Go back to the home page">
+            Node.js (1)
+          </a>
+        </div>
+        __GTOC__
       </div>
-      __GTOC__
     </div>
 
     <div id="column1" data-id="__ID__" class="interior">