refactor ActiveAdmin.flash
make ActiveAdmin.flash’s closable
close after attr for js flash messages
remove formtastic locale keys
use formtastic_i18n gem
Fix faulty placeholder in has many forms.

2133d7cdf6ec9d85406a95af9a6496306ef6492e introduced an error in all has_many forms with namespaced models.
Because ids cannot contain a forward-slash it will be rewritten by rails helpers to an underscore. So the javascript could not replace the placeholders anymore.
Added a test to capture future breaks
fix feature for devise text change
remove focus: true from some specs
use a more common initializer name
fix breadcrumb link when path passed without leading slash
Add ability to pass columns names as argument to table_for helper

```ruby
table_for user.posts, :title, :created_at do
  column :actions do |post|
    link_to 'Approve', approve_admin_posts_path(post, method: :post)
  end
end
```
Merge pull request #3469 from timoschilling/fix_specs_for_devise

fix feature for devise text change
Merge pull request #3415 from timoschilling/i18n_remove_formtastic

remove formtastic locale keys
Merge pull request #3492 from dmitry/fix/breadcrumbs-leading-slash-may-be-left

Fix breadcrumb link when path passed without leading slash
Merge branch 'pr/js_flash'
Merge branch 'pr/remove_focus'
Merge pull request #3488 from timoschilling/engine_initializer

use a more common initializer name
Merge pull request #3496 from bolshakov/feature/table_columns

Add ability to pass columns names as argument to table_for helper
Merge pull request #3460 from DiMarcello/feature/namespaced-has_many

Fix faulty placeholder in has many forms.