Feature/mad 91 gitlab pipeline

Gitlab pipeline definition for build, test + deploy. README updated with relevant information + description of steps for running the same jobs locally. Feel free to edit the README as you see fit.

.gitlab-ci.yml

@@ -3,14 +3,14 @@ default:
 
 stages:
     - build
+    - test
     - deploy
-    - pages
 
 before_script:
     - python -V
     - python -m venv venv
     - . venv/bin/activate 
-    - pip install build twine pytest
+    - pip install -e .
 
 build:
     stage: build
@@ -23,6 +23,13 @@ build:
             - dist/*.whl
         expire_in: 2 days
 
+test:
+    stage: test
+    tags:
+        - vips-runner
+    script:
+        - pytest
+
 deploy:
     stage: deploy
     tags: