Update ui.css.scss

The ui-dialog is not well rendered in version 2.1 compared to the same ui-dialog in version 2.0 : the cross on the top right side is not well positioned and the rounded corners are not rounded.

The problem is that the css didn't change between v2.0 and v2.1.

I modified the ui.css.scss to get the cross back in the good place but I didn't do anything for the rounded corners.
Merge pull request #2395 from arnie05/patch-1

Update ui.css.scss
Allow Refinery to boot using Rails 4.
Switched to ActiveSupport::Inflector#underscore as ActiveModel::Name#underscore seems to have gone
Stop using deprecation.
Stub rather than using assignment
Fixed deprecation warning by calling .find as the last method in the chain.
Github source awesome_nested_set
Use github source for orm_adapter and manually extend it because it was not doing it automatically.
Updated to support new TestCase#process API.
Use my own fork of database_cleaner.
Method calling order has changed in the find_* method so stub out these calls.
Make our overridden devise routes to be matched first.
Invoke rake tasks from system more reliably.
The result of truncate still needs to be marked html_safe.
Added launchy; Removed test gems from the development group. Support PATCH in preview route.
update_attribute was changed to update_column.
Change *args splat to options hash because we need a hash instead of array.
Correct method comment.
Update Rails 3.2 -> Rails 4.0 APIs.