Executable step by step graph processor
// Load document by HTTP
loader, _ := s.graph.SetItem("loader", loader{})
// Get links from document
links, _ := s.graph.SetItem("links", exegraph.ExecuterFnk(s.processLinks), loader)
// Process link and grab information
s.graph.SetItem("process", exegraph.ExecuterFnk(s.processDocument), loader)