To reduce new user confusion and improve intellisense/code completion, the Spine Mecanim bridge component "SkeletetonAnimator" will be renamed to "SkeletonMecanim".
As it is, "SkeletonAnimator" is currently too similar to "SkeletonAnimation" both at a glance and to component search and IDE code completion menus.
This name change will happen in a future version.
The script GUIDs will be retained so component references (and your GameObject setups) should remain intact.
But in this new version, your code will need to be updated to identify SkeletonMecanim instead of SkeletonAnimator.
Just to reiterate: This has not happened yet. This is just an announcement about a change in a future version of Spine-Unity.