Fix history pagination with paper_trail, specs

Hi!
When using PaperTrail extension, RailsAdmin::Extensions::PaperTrail::AuditingAdapter was returninig `VersionProxy` objects array:
```
versions.collect { |version| VersionProxy.new(version, @user_class) }
```
which is later used in `history` view:
```
- unless params[:all] || !@history.respond_to?(:current_page)
```
The array, returned by `collect` obviously doesn't respond to `#current_page`, as a result history pages have no pagination. Fix, and PaperTrail integration specs