Merge branch '35-spm-fix-deploy-docs-errors' into 'master'

Addresses #35 - Fixes deploy_docs confirguation by adding correct dependencies

Closes #35

See merge request flatland/flatland!21

.gitlab-ci.yml

@@ -37,6 +37,8 @@ build_and_deploy_docs:
         - tests
     before_script:
         - pip install awscli
+        - apt update
+        - apt install -y graphviz libgl1-mesa-glx xvfb xdg-utils
     script:
         - pip install -r requirements_dev.txt
         - python setup.py install