fix(empower): bugfix: power-assert output doesn't appear in Node 0.11.x

Error#stack is set in AssertionError constructor function.
So I need to instantiate another AssertionError to replace stack.

lib/decorator.js

@@ -66,29 +66,33 @@ Decorator.prototype.concreteAssert = function (invocation, context) {
 };
 
 Decorator.prototype.errorToRethrow = function (e, originalMessage, context) {
-    var f;
+    var f, attrs;
     if (e.name !== 'AssertionError') {
         return e;
     }
     if (typeof this.receiver.AssertionError !== 'function') {
         return e;
     }
-    if (isPhantom) {
-        f = new this.receiver.AssertionError({
-            actual: e.actual,
-            expected: e.expected,
-            operator: e.operator,
-            message: e.message
-        });
+
+    attrs = {
+        actual: e.actual,
+        expected: e.expected,
+        operator: e.operator,
+        message: e.message
+    };
+
+    if (this.config.modifyMessageOnRethrow) {
+        attrs.message = this.buildPowerAssertText(originalMessage, context);
+        attrs.stackStartFunction = Decorator.prototype.concreteAssert;
+    }
+
+    if (isPhantom || this.config.modifyMessageOnRethrow) {
+        f = new this.receiver.AssertionError(attrs);
     } else {
         f = e;
+        f.message = attrs.message;
     }
-    if (this.config.modifyMessageOnRethrow) {
-        f.message = this.buildPowerAssertText(originalMessage, context);
-        if (typeof e.generatedMessage !== 'undefined') {
-            f.generatedMessage = false;
-        }
-    }
+
     if (this.config.saveContextOnRethrow) {
         f.powerAssertContext = context;
     }