Add .travis.yaml to set up CI

Nothing fancy, just build the images and push them,
and if it's a push to master then also build latest.

.travis.yml

@@ -0,0 +1,19 @@
+# since everything's happening inside docker, use a generic base image
+language: minimal
+
+# enable docker
+services:
+- docker
+
+# what to actually run
+script: |
+  set -eu
+  export PUSH=true # always push
+  # if this is a push to master build, also push latest
+  if [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$TRAVIS_BRANCH" == "master" ]; then
+    export PUSH=latest
+  fi
+  # log into quay.io so we can push
+  echo "$QUAY_PASSWORD" | docker login quay.io -u "$QUAY_USER" --password-stdin
+  # build and push all components
+  ./build