Switch to 4.1

.travis.yml

@@ -4,7 +4,7 @@ before_install:
   - sudo apt-get update -q
   - sudo apt-get install -qq apt-transport-https python-docutils
   - curl https://repo.varnish-cache.org/debian/GPG-key.txt | sudo apt-key add -
-  - echo "deb https://repo.varnish-cache.org/ubuntu/ precise varnish-4.0" | sudo tee /etc/apt/sources.list.d/varnish-cache.list
+  - echo "deb https://repo.varnish-cache.org/ubuntu/ precise varnish-4.1" | sudo tee /etc/apt/sources.list.d/varnish-cache.list
   - sudo apt-get -q update
   - sudo apt-get install varnish libvarnishapi-dev