Class transform: Fix super calls and literal methods

This diff fixed two things:

1. Unqualified super calls from methods should call [1] parent methods with the same name (the bug was: they called parent constructor);

```
class A {
  foo() { console.log('A#foo'); }
}

class B extends A {
  // This method should call A#foo
  foo() { super(); }
}
```
[1] http://people.mozilla.org/~jorendorff/es6-draft.html#sec-makesuperreference

2. Fixed literal method names (the bug was: method name was compiled as `undefined`)

class A {
  'foo bar'() {}
}