Add --space-in-empty-paren (-E) option, fix #409

The following commit adds a `--space-in-empty-paren` (`-E`) option and related tests. When used in conjonction with `--space-in-paren`, its effect is to allow the following beautifying :

```js
define(function(){
    var foo=[];
    return {};
});
```

becomes

```js
define( function ( ) {
    var foo = [ ];
    return { };
} );
```

instead of

```js
define( function () {
    var foo = [];
    return {};
} );
```

Some coding styles ask for using spaces inside empty parentheses, this commit should allow to use jsbeautifier with them.

The only issue is that it adds an option. I would have liked to make `--space-in-paren` allow an option, something like `--space-in-parent=all`, but it would break BC since the following `--space-in-paren foo.js` wouldn't be correctly parsed anymore.