Migration to node 12

[UlisesGascon]

Context

• This is part of release-1.5 Roadmap for 2019-2020 #148
• Critical task

Tasks

• Add support for Node 12
• Add support for Node 10
• Add support for Node 8
• Update travis.yaml with the builds for those environments
• Update the readme.md with the relevant info

Assignation

• This tasks is open for assignation, just claim it (as reply to this) and submit your PR ;-)

Important

• Check the current roadmap Roadmap for 2019-2020 #148
• Don't forget to check the Contributing Guidelines and follow the Code of Conduct

[binarymist]

Pretty sure last time I suggested we upgrade @ckarande wasn't that keen. Hopefully this has changaed?

[ckarande]

@binarymist Yes, I know this item has been in the list for a while. I am good to take it now. Having the integration test coverage now allows us to do the necessary validations in an efficient way. 👍

[UlisesGascon]

This was closed by #160