1.x-3.0.0-beta-3

Changes since 1.x-3.0.0-beta-2:

• 6585b82 Style details element to match fieldset styling. by @laryn
• 9240a69 Fix error background color in admin toolbar. by @laryn
• Issue #132: Adapt for upcoming core admin menu changes in 1.28.0. by @laryn

Full Changelog: 1.x-3.0.0-beta-2...1.x-3.0.0-beta-3