integrate DOT with markdown for graph
I diged but not found gitlab-ce can easily draw charts.
DOT (graph description language) is really useful for charts like flow chart / ER chart / class diagrams.
Although it's ability limited in drawing sequence chart. I suggest it for mark down documents.
Links / references
[what is dot (wiki)| https://en.wikipedia.org/wiki/DOT_(graph_description_language)]
[use graphviz dot for uml diagrams | http://www.ffnn.nl/pages/articles/media/uml-diagrams-using-graphviz-dot.php]`