New feature: TabPane can be focused and navigated by keyboard

The focused state of a TabPane can be styled using properties that apply
to the active tab.
Fix minor error leading to build-failure with JSLint.
Merge branch 'feature/focusable-tab-pane' into stable-3.0.x
Prepare v3.0.1 release
Merge tag 'v3.0.1' into stable-3.0.x