Plural of specimen

I'm having an issue with getting the inflector to accept that the plural of specimen as specimens.

Using:
```javascript
const inflector = Inflector.inflector;
inflector.irregular('specimen', 'specimens');
```
Is not working for me, it still reports back specimen.

```
{{pluralize "specimen"}} -> specimen
```
However, if I change specimens to mens

```javascript
inflector.irregular('men', 'mens');
```
```
{{pluralize "specimen"}} -> specimens
```
I believe this is to do with specimens being treated as a compound noun.

In addition using, it as an irregular inflection works in Rails.