travis docker layers cache

.travis.yml

@@ -15,7 +15,7 @@ env:
 cache:
   bundler: true
   directories:
-    - $HOME/docker
+    - /var/lib/docker/
 
 jobs:
   include:
@@ -83,15 +83,6 @@ jobs:
       before_script:
         - ARCH=armhf
               
-      before_cache:
-        # Save tagged docker images
-        - >
-          mkdir -p $HOME/docker && docker images -a --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
-      
       script:
         # prepare qemu
         - docker run --rm --privileged multiarch/qemu-user-static:register --reset