Fix broken cases for AlignDoubleArrowFixer

Maybe try bottom-up approach?
Take a look at MultilineArrayTrailingCommaFixer (add comma after last element of multi-line array).
How we fix a following code:
```php
    $a = array(
        1 => array(
            2 => 3
        )
    );',
```

We iterate backwards, thus we first encounter nested array, and then the main one.
So first - we met opening of nested array and we simply add a comma after `2 =>3` part:
```php
    $a = array(
        1 => array(
            2 => 3,
        )
    );',
```
Then we met opening of main array and completely ignore the fact it contains array - just like it would be any simple content that no need to be fixed:
```php
    $a = array(
        1 => SOME_VALUE
    );',
```
Then we have same situation like at beginning and we simply add comma after last array value.

That approach allows us to keep the code clean and simple - and what's more to fix nested structures of any level.

I hope you will find this helpful...