When I upgraded to D8 alpha 14, the three tabs that I had implemented for the module disappeared. The paths still worked since the forms were accessible by using the address field of the browser.
A search on the core .yml files in D8 alpha 13 compared with alpha 14 suggested that the *.local_tasks.yml files that were used to define groups of tabs for the same "page" had been renamed to *.links.task.yml instead.
When I renamed optimizely.local_tasks.yml to optimizely.links.task.yml, the tabs were rendered again.
The source article below later confirmed this hunch.
Previous post on the format and contents of this file is at http://optimizely-to-drupal-8.blogspot.com/2014/05/implementing-multiple-tabs-on-page.html
YAML files for menu links, contextual links, local tasks, and local actions have been renamed