The default FirefoxDriver from Selenium no longer supports Firefox since
version 47 without a native web driver. This commit adds support to
native drivers, downloading and configuring this drivers depending on
the current OS (only Unix, Windows and Mac OS supported at this moment).

The REST layer has been added but with incomplete tests. Students will
have to complete the tests.

This commit includes an important refactorization regarding tests. Test
classes and datasets have been moved from the "service" project to a new
"tests" project. This way, any project can include this "tests" project
as a dependency in order to have access to these common testing
resources.

Initial commit with a basic .gitignore, README.md and POM files.