Add GraphContext class, which output a graphviz file of dependendencies in stdout
Render a parameter setting on each node
Improves output format
Add a command description
Add a document
Output dot file when the suffix of output path is .dot
Fix a bug in older graphviz (requiring escaping for new lines)
A import statement is moved
A import statement is moved
Merge pull request #64 from nozyh/feature/graph_context

Feature/graph context