Add vulcanize to tools.

tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/cheerio-select/node_modules/CSSselect/node_modules/domutils/lib/helpers.js

Index: tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/cheerio-select/node_modules/CSSselect/node_modules/domutils/lib/helpers.js
diff --git a/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/cheerio-select/node_modules/CSSselect/node_modules/domutils/lib/helpers.js b/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/cheerio-select/node_modules/CSSselect/node_modules/domutils/lib/helpers.js
new file mode 100644
index 0000000000000000000000000000000000000000..476b8eb51b67247c802ad3a77d18ab4266bbb3b7
--- /dev/null
+++ b/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/cheerio-select/node_modules/CSSselect/node_modules/domutils/lib/helpers.js
@@ -0,0 +1,31 @@
+// removeSubsets
+// Given an array of nodes, remove any member that is contained by another.
+exports.removeSubsets = function(nodes) {
+	var idx = nodes.length, node, ancestor, replace;
+
+	// Check if each node (or one of its ancestors) is already contained in the
+	// array.
+	while (--idx > -1) {
+		node = ancestor = nodes[idx];
+
+		// Temporarily remove the node under consideration
+		nodes[idx] = null;
+		replace = true;
+
+		while (ancestor) {
+			if (nodes.indexOf(ancestor) > -1) {
+				replace = false;
+				nodes.splice(idx, 1);
+				break;
+			}
+			ancestor = ancestor.parent;
+		}
+
+		// If the node has been found to be unique, re-insert it.
+		if (replace) {
+			nodes[idx] = node;
+		}
+	}
+
+	return nodes;
+};