Tab name not translated

On initializing the PageImage extension it says:

```
def self.register(tab)
    tab.name = ::I18n.t(:'refinery.plugins.refinery_page_images.tab_name')
    tab.partial = "/refinery/admin/pages/tabs/images"
end
```

Unfortunately the tab.name is not correctly translated as the preferred locale has not yet been set. It keeps showing 'Images' while my locale has been set to :nl. 