[WIP] Added ADD/PREPEND Tags for Events

@@ -129,6 +129,51 @@ EventEmitter.prototype.addListener = function addListener(type, listener) {
   } else if (isArray(this._events[type])) {
 
     // If we've already got an array, just append.
+    this._events[type].push(listener);
+
+    // Check for listener leak
+    if (!this._events[type].warned) {
+      var m;
+      if (this._maxListeners !== undefined) {
+        m = this._maxListeners;
+      } else {
+        m = defaultMaxListeners;
+      }
+
+      if (m && m > 0 && this._events[type].length > m) {
+        this._events[type].warned = true;
+        console.error('(node) warning: possible EventEmitter memory ' +
+                      'leak detected. %d listeners added. ' +
+                      'Use emitter.setMaxListeners() to increase limit.',
+                      this._events[type].length);
+        console.trace();
+      }
+    }
+  } else {
+    // Adding the second element, need to change to array.
+    this._events[type] = [this._events[type], listener];
+  }
+
+  return this;
+};
+
+EventEmitter.prototype.prependListener = function prependListener(type, listener) {
+  if ('function' !== typeof listener) {
+    throw new CasperError('addListener only takes instances of Function');
+  }
+
+  if (!this._events) this._events = {};
+
+  // To avoid recursion in the case that type == "newListeners"! Before
+  // adding it to the listeners, first emit "newListeners".
+  this.emit('newListener', type, listener);
+
+  if (!this._events[type]) {
+    // Optimize the case of one listener. Don't need the extra array object.
+    this._events[type] = listener;
+  } else if (isArray(this._events[type])) {
+
+    // If we've already got an array, just append.
     this._events[type].unshift(listener);
 
     // Check for listener leak
@@ -157,7 +202,20 @@ EventEmitter.prototype.addListener = function addListener(type, listener) {
   return this;
 };
 
-EventEmitter.prototype.on = EventEmitter.prototype.addListener;
+EventEmitter.prototype.on = function on(type, listener, tag) {
+    switch(tag) {
+        case "ADD":
+        return this.addListener(type, listener);
+        break;
+
+        case "PREPEND":
+        return this.prependListener;
+        break;
+
+        default:
+        return this.addListener(type, listener);
+    }
+};
 
 EventEmitter.prototype.once = function once(type, listener) {
   if ('function' !== typeof listener) {

@@ -1532,7 +1532,7 @@ Tester.prototype.renderResults = function renderResults(exit, status, save) {
 };
 
 /**
- * Runs al suites contained in the paths passed as arguments.
+ * Runs all suites contained in the paths passed as arguments.
  *
  */
 Tester.prototype.runSuites = function runSuites() {