[ci skip] remove unused travis.yml file

We are now using CircleCI for testing dokku

.travis.yml

@@ -1,16 +0,0 @@
----
-branches:
-  only:
-    - master
-script:
-  - echo "StrictHostKeyChecking=no" >> ~/.ssh/config
-  - export IP=$(curl -s http://dokku-ci.herokuapp.com/hosts | tail -1)
-  - git config --global user.email "travis-ci@exmaple.com"
-  - git config --global user.name "Travis CI"
-  - git checkout --orphan orphan HEAD
-  - git commit -am 'orphaned'
-  - git remote add runner ssh://test@$IP:2022/dokku
-  - sleep 8
-  - git push runner orphan:master
-notifications:
-  irc: "chat.freenode.net#dokku"