Add vulcanize to tools.

tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/htmlparser2/node_modules/readable-stream/lib/_stream_duplex.js

Index: tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/htmlparser2/node_modules/readable-stream/lib/_stream_duplex.js
diff --git a/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/htmlparser2/node_modules/readable-stream/lib/_stream_duplex.js b/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/htmlparser2/node_modules/readable-stream/lib/_stream_duplex.js
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index 0000000000000000000000000000000000000000..a2e0d8e0dac03688a882bad193681e7601671738
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+++ b/tools/vulcanize/node_modules/vulcanize/node_modules/cheerio/node_modules/htmlparser2/node_modules/readable-stream/lib/_stream_duplex.js
@@ -0,0 +1,69 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+// a duplex stream is just a stream that is both readable and writable.
+// Since JS doesn't have multiple prototypal inheritance, this class
+// prototypally inherits from Readable, and then parasitically from
+// Writable.
+
+module.exports = Duplex;
+var util = require('util');
+var Readable = require('./_stream_readable');
+var Writable = require('./_stream_writable');
+
+util.inherits(Duplex, Readable);
+
+Object.keys(Writable.prototype).forEach(function(method) {
+  if (!Duplex.prototype[method])
+    Duplex.prototype[method] = Writable.prototype[method];
+});
+
+function Duplex(options) {
+  if (!(this instanceof Duplex))
+    return new Duplex(options);
+
+  Readable.call(this, options);
+  Writable.call(this, options);
+
+  if (options && options.readable === false)
+    this.readable = false;
+
+  if (options && options.writable === false)
+    this.writable = false;
+
+  this.allowHalfOpen = true;
+  if (options && options.allowHalfOpen === false)
+    this.allowHalfOpen = false;
+
+  this.once('end', onend);
+}
+
+// the no-half-open enforcer
+function onend() {
+  // if we allow half-open state, or if the writable side ended,
+  // then we're ok.
+  if (this.allowHalfOpen || this._writableState.ended)
+    return;
+
+  // no more data can be written.
+  // But allow more writes to happen in this tick.
+  process.nextTick(this.end.bind(this));
+}