Migration to es6+

[UlisesGascon]

Context

• This is part of release-1.5 Roadmap for 2019-2020 #148
• Depends on Migration to node 12 #150
• Critical task

Tasks

• Clean Source code (JS Files)
• Migrate to ES6+ Syntaxis (Promises, Async, const/let, arrow...)
• Update the readme.md with the relevant info (if needed)

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

[lucas1004jx]

I want to help with this issue :)

[UlisesGascon]

Thanks @lucas1004jx for join us! 🤗

This issue is assigned to you, please remember to refer to this issue when do you submit a PR, so we can connect the dots easily.