Fix JUnit vintage tests and add vintage engine

[tonilopezmr]

📌 References

• Related pull-requests: Add JUnit 5 support #52 Use more conventional diff colouring #54

🎩 What is the goal?

• Run JUnit 5 and JUnit Vintage (JUnit4) tests
• Fix JUnit4 test didn't update in Use more conventional diff colouring #54

📝 How is it being implemented?

• Upgrade gradlew version
• Replaced compile to implementation method
• Add JUnit Vintage engine which is responsible to run find and run JUnit 4 tests, this error was introduced in the last commit of the PR Add JUnit 5 support #52

💥 How can it be tested?

• Now in Travis runs all JUnit tests

I'd like to improve the Travis output because I can't see the test output easily

[pedrovgs]

Thanks for the PR @tonilopezmr. I've tested this branch manually and it works like a charm. I can see a new screenshot I was missing in the original PR where that test was added.

[pedrovgs]

I'm going to merge this PR because the author of the PR is one of our core committers, @Serchinastico is out for holidays and @flipper83 he's busy with other tasks.

[tonilopezmr]

Thanks!! 👍