Use gremlin-v3 v0.0.5
Use forEach to implement Gremlin traversal iteration.
Obtain Direction enum from Gremlin object.
Save the options block in the GraphvizGraph.
Add 'doc' script to generate source code documentation with Docco.
Add vertexId option to specify alternate vertex label.

Creates a new "util" submodule that will contain useful but optional parts of the
API.
Allow Graphviz edge labels based on Gremlin edge labels.
Doc tweaks
Merge pull request #4 from mhfrantz/feature/Decoration-of-graph-visualization_83530752

[Delivers #83530752] Decoration of graph visualization