Finalise Release Pipeline

[rrmerugu]

Notes of how the release flow should look like for this project.

• [ ] on Pull Request (to Master)
  • [ ] deploy a graph-explorer-edge application on Heroku
• [ ] on Push/Merge (to Master)
  • [ ] generate and push build to docker registry
  • [ ] deploy latest version to heroku

[rrmerugu]

added https://github.com/invanalabs/graph-explorer/blob/develop/.travis.yml