Update .gitlab-ci.yml

.gitlab-ci.yml

-#This declares the pipeline stages  
-build_image:
+docker-build-master:
+  # Official docker image.
+  image: docker:latest
+  stage: build
+  services:
+    - docker:dind
+  before_script:
+    - docker login -u "$CI_REGISTRY_USER" -p "$CI_REGISTRY_PASSWORD" $CI_REGISTRY
   script:
-    - docker login -u gitlab-ci-token -p $CI_BUILD_TOKEN $CI_REGISTRY
-    - docker build -t $CI_REGISTRY_IMAGE .
-    - docker push $CI_REGISTRY_IMAGE
+    - docker build --pull -t "$CI_REGISTRY_IMAGE" .
+    - docker push "$CI_REGISTRY_IMAGE"
   only:
     - master
- 
   tags:
-    - general
-  
+    - docker