Prevent active admin framework dialog styling from clobbering all jQuery UI dialogs.
Only namespace the destructive style change.

The other defaults seem like a good idea to apply globally.
changed rspec syntax `stub` to `allow`
Merge pull request #3174 from Squeegy/master

Prevent active admin from clobbering all jQuery UI dialog close buttons
add unit test for ActiveAdmin::DSL #sidebar

ref: #3178
Merge pull request #3175 from enbaglisash/patch

changed rspec syntax `stub` to `allow`