Standarize test cases and testing

[marcosfede]

We should standarize the way we write test cases across problems and across languages.
It would also be nice to have some sort of CI Pipeline and make the code run the tests to make sure solutions are functional

[marcosfede]

We should add basic linting tests to the travis pipeline for Each language. This is currently only implemented for Python

[marcosfede]

Added linters for JS and Ruby to the Travis pipeline. We should add linters for Go and Scala next