Adds a vertex with the given name, or updates the existing one. @param [String] name @param [Object] payload @return [Vertex] the
vertex that was added to `self`
# File lib/rubygems/resolver/molinillo/lib/molinillo/dependency_graph.rb, line 160
def add_vertex(name, payload, root = false)
log.add_vertex(self, name, payload, root)
end
