Update .gitlab-ci.yml

.gitlab-ci.yml

 image: ruby:2.3
 
-build:
+stages:
+- build
+- test
+
+build_job:
   stage: build
   script:
     - bash ci-build.sh
 
 # run tests using the binary built before
-test:
+test_job:
   stage: test
   script:
     - bash ci-test.sh