Util: Move toc ID in parseMarkdown from icon to heading

Currently, the heading IDs are not actually on the heading
elements. This means that scrapers such as Algolia and
Typesense often link text excerpts under a heading to
something far away like `#content` instead of the nearest
preceeding heading.

For semantics, and to benefit search suggestions, I think the
heading IDs are better suited on headings.

Closes gh-90
Ref jquery/infrastructure-puppet#33

Author: Krinkle

lib/util.js

@@ -47,8 +47,8 @@ function parseMarkdown( src, options ) {
 		item.pre = false;
 
 		// Insert the link
-		item.text = "<h" + item.depth + " class='toc-linked'>" +
-			"<a href='#" + item.tocId + "' id='" + item.tocId + "' class='icon-link toc-link'>" +
+		item.text = "<h" + item.depth + " class='toc-linked' id='" + item.tocId + "'>" +
+			"<a href='#" + item.tocId + "' class='icon-link toc-link'>" +
 				"<span class='visuallyhidden'>link</span>" +
 			"</a> " + parsedText + "</h" + item.depth + ">";