(Refactor) Make redis storage files to use promises

[garatortiz]

• What is it? (leave one option)

  • (Refactor) of existing code (no functionality change)

• What was the root cause of the problem originally / what feature was missing? On PR #30 was refactored the session-storage 'memory', so this PR makes Redis methods as promise to get the same output that in Memory.

• How does this pull request solve it (in broad terms)? Promisify Redis methods to get the same output that in Memory.

• Does it close any open issues? Closes #35

• Quick checklist

  • [ ] eslint shows no errors

    cd web-dapp
    eslint .

  • [ ] docs were updated where necessary OR they don't need to be updated
  • [ ] tests were updated where necessary OR they don't need to be updated

• Additional information

[phahulin]

Closes #35

[phahulin]

Should we also promisify set method?

[garatortiz]

Sure... i'll think to do it then when I'll refactor the route that use it, but yes... I'm going to do that and update the PR.