test(tabs): get test coverage to 100%

- Add one removal of a non-last tab to test one last branch
- This excludes the deprecation message for the tabs directive.
refactor(tabs): remove unused tabs directive
chore(tabs): Add tests for nested tabs

Relates to #783
fix(tabs): make nested tabs work

This reverts commit 220e7b60124105aca25e57c3f01a22e12fa77cc2.

Revert the capability to set the tab direction. This is no longer a
feature in Bootstrap 3 and breaks nested tabs.

Closes #783
Relates to #659
fix(carousel): cancel timer on scope destruction

Closes #1414
refactor(carousel): remove duplicate code

Move go function out of restartTimer as it doesn't need to be re-created
during each interval.