Add jest tests

[TiagoGouvea]

• Implement a simple jest test to validate ao requests we will have
• Add on reamed how to run tests (one line explanation)
• For testing purposes, we could have a .gitignore file somewhere with the secret data needed to run the tests

Method testing

• Each method will have a single test file, ensuring that: received status 200, the returned data is right and the attributes needed are there

Error testing

• Create a error testing file, to ensure the error responses, calling without autentication data (401), invalid params (400), 403 and 404