Removed docker caching and fixed build docker label

.travis.yml

@@ -1,21 +1,6 @@
 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
@@ -24,7 +9,7 @@ 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
+      - docker run --rm $DOCKER_USERNAME/teaweb:build /bin/bash -c /root/build_teaweb.sh travis
       if: branch = master
     - stage: test teaweb build
       script: