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

git-subtree-dir: maint-travis-ci
git-subtree-split: 75aad7e8ef3a8deab32cde7c352ccaf3781dae63
Merge commit 'e7be2a99da44b81fdcf6d2c31de6bc9bda4a1672' as 'maint-travis-ci'
Enable travis