Tried to cache travis build docker

.travis.yml

@@ -1,6 +1,21 @@
 sudo: true
 dist: trusty
 
+cache:
+  bundler: true
+  directories:
+  - $HOME/docker
+
+before_cache:
+# Save tagged docker images
+- >
+  mkdir -p $HOME/docker && docker images -a --filter='dangling=false' --format '{{.Repository}}:{{.Tag}} {{.ID}}'
+  | xargs -n 2 -t sh -c 'test -e $HOME/docker/$1.tar.gz || docker save $0 | gzip -2 > $HOME/docker/$1.tar.gz'
+
+before_install:
+# Load cached docker images
+- if [[ -d $HOME/docker ]]; then ls $HOME/docker/*.tar.gz | xargs -I {file} sh -c "zcat {file} | docker load"; fi
+
 jobs:
   include:
     - stage: build teaweb
@@ -9,9 +24,9 @@ jobs:
       - docker images
       - docker pull $DOCKER_USERNAME/teaweb:build
       - docker images
-      - docker run --rm $DOCKER_USERNAME/teaweb /bin/bash -c /root/build_teaweb.sh "travis" "travis" "travis" "travis"
+      - docker run --rm $DOCKER_USERNAME/teaweb /bin/bash -c /root/build_teaweb.sh travis
       if: branch = master
-    - stage: test teaweb
+    - stage: test teaweb build
       script:
       - echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin
       - docker images