replaced array_merge_recursive with array_replace_recursive

`array_merge_recursive` creates many issues with the config. `array_replace_recursive` resolves these issues and is meant to merge config arrays. Requires PHP 5.3+ 

Examples:

```php
/* Setting custom "supports" */
$customize = array(
  'supports' => array( 'title', 'thumbnail' ),
);
$result = array_merge_recursive(array(
  'supports'  => array( 'title', 'editor', 'thumbnail', 'revisions', 'excerpt', 'page-attributes' ),
), $customize);

/* 
Expected result:
array(
  'supports'  => array( 'title', 'thumbnail' ),
)

Actual result:
array(
  'supports'  => array( 'title', 'editor', 'thumbnail', 'revisions', 'excerpt', 'page-attributes' ),
)
*/

/* Setting custom "has_archive" */
$customize = array(
  'has_archive' => 'recordings',
);
$result = array_merge_recursive(array(
  'has_archive' => true,
), $customize);

/* 
Expected result:
array(
 'has_archive' => 'recordings'
)

Actual result:
array(
 'has_archive' => array(
   true,
   'recordings'
 )
)
*/