add build stage in CI

.gitlab-ci.yml

@@ -5,9 +5,13 @@ before_script:
   - python --version
   - pytest --version
   - pwd
-  - python swf2userSessions/swf2sessions.py --help
   - pip3 install networkx
 
+build:
+  stage: build
+  script:
+    - pip3 install .
+
 test:
   stage: test
   coverage: '/(?i)total.*? (100(?:\.0+)?\%|[1-9]?\d(?:\.\d+)?\%)$/'