Feature/i18n

**Note:** This PR goes into the Resurrection https://github.com/varvet/godmin/pull/5 branch.

### Translations
Adds translations for:
- [x] Scopes
- [x] Batch actions (Buttons, actions and confirm message)
- [x] Filters (Both buttons and labels/placeholders)
- [x] Column actions (Buttons and confirm message) Also turns the links into pretty buttons.
- [x] Actions (Create button on index page)
- [x] Sign out
- [x] Tests (Do we want tests for this?)
- [x] Reviewed

Most translations can be translated per resource, but also globally. So, let's say you want the delete action in the column to say `Nuke it!` for the Article resource but `Remove!` for all other resources (It is called `Destroy` by default). This is how you achieve that in your locale file:

```
en:
  godmin:
    column_actions:
      destroy: Remove! # This is global
    article:
      column_actions:
        destroy: Nuke it! # Applies to articles only
```

### Select2
Replaces Chosen with Select2. It also includes lots of translations for Select2 which the user may include themselves.