Implement all CI in Gitlab

- Use a matrix to test on py 3.6-3.9
- Add doc test and deployment
- Add flake8 test

.gitlab-ci.yml

@@ -1,9 +1,63 @@
-nodb:
-  stage: test
-  image:
-    name: registry.gitlab.com/taurus-org/taurus-docker:nodb
-  before_script:
-    - pip install -e .
-  script:
-    - pytest -n3 --forked -v lib/taurus
+variables:
+    DEFAULT_PY_VERSION: "3.9"
+
+
+doc:
+    # build docs
+    stage: test
+    image:
+        name: registry.gitlab.com/taurus-org/taurus-docker:nodb-$DEFAULT_PY_VERSION
+    variables:
+        PUBLIC_URL: /-/$CI_PROJECT_NAME/-/jobs/$CI_JOB_ID/artifacts/public
+    before_script:
+        - pip install sphinx sphinx-rtd-theme
+    script:
+        - xvfb-run sphinx-build -qW doc/source/ public
+    artifacts:
+        paths:
+            - public
+    environment:
+        name: Docs-dev
+        url: "https://$CI_PROJECT_NAMESPACE.gitlab.io/-/$CI_PROJECT_NAME/-/jobs/$CI_JOB_ID/artifacts/public/index.html"
+
+
+tests:
+    # run test suite with various py versions
+    parallel:
+        matrix:
+            - PY_VERSION: ["3.6", "3.7", "3.8", "3.9"]
+    stage: test
+    image:
+        name: registry.gitlab.com/taurus-org/taurus-docker:nodb-$PY_VERSION
+    before_script:
+        - pip install -e .
+    script:
+        - pytest -n3 --forked -v lib/taurus
+
+
+flake8:
+    # check style with flake8
+    allow_failure: true
+    stage: test    
+    image:
+        name: python:3.9-alpine
+    before_script:
+        - pip install flake8
+    script:
+        - flake8 .
+
+
+pages:
+    # deploy docs
+    stage: deploy
+    script:
+        - echo "deploying already-built docs "
+    artifacts:
+        paths:
+            - public
+    only:
+        variables:
+            - $CI_COMMIT_TAG =~ /^[0-9]+\.[0-9]+\.[0-9]+.*$/
+
+