Revert "apt removed from script"

This reverts commit d49b4b64.

.gitlab-ci.yml

 # In case something goes horribly wrong, you can fall back to `image: ruby:latest`
-image: git-r3lab.uni.lu:4567/r3/docker/jekyll-lcsb:1.0
+image: git-r3lab.uni.lu:4567/r3/docker/jekyll-lcsb:1.5
 
 build:
   stage: build
@@ -18,6 +18,20 @@ build:
   variables:
     JEKYLL_ENV: production
 
+
+test_spell_check:
+  image: debian
+  stage: test
+  dependencies:
+     - build
+  script:
+  - apt-get update
+  - apt-get install -y aspell aspell-en
+  - ./test_spell_check.sh
+  except:
+  - master
+
+
 pages:
   stage: deploy
   only: