Update .gitlab-ci.yml

.gitlab-ci.yml

-image: node:4.2.2
+image: node:8.11.2
 
-pages:
-  cache:
+cache:
     paths:
         - node_modules/
 
-  script:
+variables:
+    GIT_SUBMODULE_STRATEGY: recursive
+
+before_script:
     - npm install hexo-cli -g
     - npm install
-  - hexo deploy
+
+pages:
+    script:
+        - hexo generate
     artifacts:
         paths:
             - public