Fix broken CI, proofread Substrate article

This updates jinja, and markupsafe, to avoid following error:

ImportError: cannot import name 'soft_unicode' from 'markupsafe'

• Bump Pelican version
• Fix path specification parsing
• Proofread Substrate article

.gitlab-ci.yml

@@ -13,7 +13,7 @@ build-job:
     - mkdir -p /usr/share/man/man1 # Because of https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=863199
     - apt-get update && apt-get install -y plantuml graphviz
     - pip install -r requirements.txt
-    - pelican content -s publishconf.py -e OUTPUT_PATH=public/
+    - pelican content -s publishconf.py -e OUTPUT_PATH='"public"'
   artifacts:
     paths:
       - public/