Update .travis.yml

.travis.yml

@@ -10,11 +10,22 @@ addons:
 notifications:
   email:
   - team@appwrite.io
-
+  
 services:
 - docker
 
+before_cache:
+  - >
+    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'
+  
+cache:
+  bundler: true
+  directories:
+    - $HOME/docker
+
 before_install:
+- if [[ -d $HOME/docker ]]; then ls $HOME/docker/*.tar.gz | xargs -I {file} sh -c "zcat {file} | docker load"; fi
 - composer update --ignore-platform-reqs --optimize-autoloader --no-plugins --no-scripts
 - sudo service mysql stop
 
@@ -24,4 +35,4 @@ install:
 
 script:
 - docker ps
-- vendor/bin/phpunit --configuration phpunit.xml
+- vendor/bin/phpunit --configuration phpunit.xml