attempt to remove gomod (#71)

Replace travis job with github action. (#66)

* Replace travis job with github action.

* Add action rule in Makefile to perform the same steps as github action.
Github actions also run on pull_request.
Add help option to Makefile.

* Add missing regenerate step.

Merge branch 'master' of github.com:awalterschulze/gographviz

upgrade go version

Make cluster subgraphs as nodes for edges 2 (#24)

* Make cluster subgraphs as nodes for edges

* Add test for cluster subgraphs

* update grammar to handle subgraphs without statements

replaced drone with travis