v11.3.3

No functional or code changes to the release, though it now explicitly supports Ubuntu Xenial stemcells. No changes to the release itself were necessary to achieve this support. The release has worked with Xenial for some time.

There are changes in the test and CI code to make the tests work across multiple stemcells (and work with Xenial at all). The release is now continuously tested against both Trusty and Xenial.

In particular, it's now possible to set STEMCELL_OS as an environment variable,
and run the acceptance tests with an arbitrary stemcell.
It gets interpolated into the test manifests.
Any value that's valid for os in the manifest should work.

Also, the version of Go used is now 1.11.