use mermaidAPI

[piranna]

mermaid now has an offline render that directly returns a SVG image. By using it, we could be able to remove all the dependencies on PhantomJS and make the module a lot more simpler and faster :-)

[JozoVilcek]

I do not think so, that API assumes it runs in browser (or equivalent) which does heavy lifting in svg rendering. It is not replacing mermaidCLI