Fix the generated AST.

Recast just happens to print the old version correctly, but it was
actually wrong. If you had `[].slice.call(arguments, 2)` the structure
of that AST would look like:

```
CallExpression
  MemberExpression
    MemberExpression
      ArrayExpression
      Identifier slice
    Identifier call
  Identifier arguments
  Literal 2
```

So I've updated the structure to be like that.