Squashed 'maint-travis-ci/' content from commit 75aad7e

git-subtree-dir: maint-travis-ci
git-subtree-split: 75aad7e8ef3a8deab32cde7c352ccaf3781dae63
Merge commit '9fb32311209faf6994ad0964a8e4da2677836b28' as 'maint-travis-ci'
Enable travis