Index: frontend/node_modules/on-headers/index.js
===================================================================
--- frontend/node_modules/on-headers/index.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
+++ frontend/node_modules/on-headers/index.js	(revision 9af201e94b5a79beb92a30858fc54de4bc3b9449)
@@ -0,0 +1,180 @@
+/*!
+ * on-headers
+ * Copyright(c) 2014 Douglas Christopher Wilson
+ * MIT Licensed
+ */
+
+'use strict'
+
+/**
+ * Module exports.
+ * @public
+ */
+
+module.exports = onHeaders
+
+var http = require('http')
+
+// older node versions don't have appendHeader
+var isAppendHeaderSupported = typeof http.ServerResponse.prototype.appendHeader === 'function'
+var set1dArray = isAppendHeaderSupported ? set1dArrayWithAppend : set1dArrayWithSet
+
+/**
+ * Create a replacement writeHead method.
+ *
+ * @param {function} prevWriteHead
+ * @param {function} listener
+ * @private
+ */
+
+function createWriteHead (prevWriteHead, listener) {
+  var fired = false
+
+  // return function with core name and argument list
+  return function writeHead (statusCode) {
+    // set headers from arguments
+    var args = setWriteHeadHeaders.apply(this, arguments)
+
+    // fire listener
+    if (!fired) {
+      fired = true
+      listener.call(this)
+
+      // pass-along an updated status code
+      if (typeof args[0] === 'number' && this.statusCode !== args[0]) {
+        args[0] = this.statusCode
+        args.length = 1
+      }
+    }
+
+    return prevWriteHead.apply(this, args)
+  }
+}
+
+/**
+ * Execute a listener when a response is about to write headers.
+ *
+ * @param {object} res
+ * @return {function} listener
+ * @public
+ */
+
+function onHeaders (res, listener) {
+  if (!res) {
+    throw new TypeError('argument res is required')
+  }
+
+  if (typeof listener !== 'function') {
+    throw new TypeError('argument listener must be a function')
+  }
+
+  res.writeHead = createWriteHead(res.writeHead, listener)
+}
+
+/**
+ * Set headers contained in array on the response object.
+ *
+ * @param {object} res
+ * @param {array} headers
+ * @private
+ */
+
+function setHeadersFromArray (res, headers) {
+  if (headers.length && Array.isArray(headers[0])) {
+    // 2D
+    set2dArray(res, headers)
+  } else {
+    // 1D
+    if (headers.length % 2 !== 0) {
+      throw new TypeError('headers array is malformed')
+    }
+
+    set1dArray(res, headers)
+  }
+}
+
+/**
+ * Set headers contained in object on the response object.
+ *
+ * @param {object} res
+ * @param {object} headers
+ * @private
+ */
+
+function setHeadersFromObject (res, headers) {
+  var keys = Object.keys(headers)
+  for (var i = 0; i < keys.length; i++) {
+    var k = keys[i]
+    if (k) res.setHeader(k, headers[k])
+  }
+}
+
+/**
+ * Set headers and other properties on the response object.
+ *
+ * @param {number} statusCode
+ * @private
+ */
+
+function setWriteHeadHeaders (statusCode) {
+  var length = arguments.length
+  var headerIndex = length > 1 && typeof arguments[1] === 'string'
+    ? 2
+    : 1
+
+  var headers = length >= headerIndex + 1
+    ? arguments[headerIndex]
+    : undefined
+
+  this.statusCode = statusCode
+
+  if (Array.isArray(headers)) {
+    // handle array case
+    setHeadersFromArray(this, headers)
+  } else if (headers) {
+    // handle object case
+    setHeadersFromObject(this, headers)
+  }
+
+  // copy leading arguments
+  var args = new Array(Math.min(length, headerIndex))
+  for (var i = 0; i < args.length; i++) {
+    args[i] = arguments[i]
+  }
+
+  return args
+}
+
+function set2dArray (res, headers) {
+  var key
+  for (var i = 0; i < headers.length; i++) {
+    key = headers[i][0]
+    if (key) {
+      res.setHeader(key, headers[i][1])
+    }
+  }
+}
+
+function set1dArrayWithAppend (res, headers) {
+  for (var i = 0; i < headers.length; i += 2) {
+    res.removeHeader(headers[i])
+  }
+
+  var key
+  for (var j = 0; j < headers.length; j += 2) {
+    key = headers[j]
+    if (key) {
+      res.appendHeader(key, headers[j + 1])
+    }
+  }
+}
+
+function set1dArrayWithSet (res, headers) {
+  var key
+  for (var i = 0; i < headers.length; i += 2) {
+    key = headers[i]
+    if (key) {
+      res.setHeader(key, headers[i + 1])
+    }
+  }
+}