[BUGFIX] Call parent constructor with derived arguments if no derived constructor is provided

Right now, the parent class constructors aren't being called with the callee's arguments if no constructor is provided in the derived.

```javascript
class Person {
  constructor(name) {
    this.name = name;
  }

  say(msg) {
    console.log(this.name + " says: " + msg);
  }
}

class Bob extends Person {
  
}

var bob = new Bob("Bob");
bob.say("Macros are sweet!");
// Currently logs "undefined says: Macros are sweet!"
```

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-class-definitions#sec-runtime-semantics-classdefinitionevaluation

![image](https://cloud.githubusercontent.com/assets/762949/3062082/c139f1cc-e215-11e3-8135-7b29846eed34.png)