Missing irregular rule for gloves

```php
Inflector::singularize('gloves');
```
Should return "glove" but instead returns "glofe".

This is fixable by adding the following line:
```php
->irregular('glove', 'gloves')
```
after
```php
->irregular('zombie', 'zombies')
```

in `lib/Inflections/en.php` inside the function body for the `configure()` method.
