Added automatic testing of snip-tags

.gitlab-ci.yml

@@ -3,7 +3,7 @@ image: ubuntu:latest
 stages:
   - test
 
-.test_snipper:
+test_snipper:
   stage: test
   script:
     - echo "Testing student files"
@@ -26,6 +26,3 @@ stages:
     - latexmk --version
     - ls tests_images/*
 
-test_39:
-  extends: .test_students
-  image: ubuntu:latest