Ignoring maven target files
Correcting gitignore
finally gitignore is working
Refactoring StringReverser
Testing that an object put in a HashMap can be retrieved using get.
HashMap: Testing that adding a value to an existent key updates the valeu.
Refactoring tests.
HashMap: Testing that clear() removes all its content.
HashMap: Testing that null can be used as a key.
Copying Fahrenheit to Celsius conversion test from the book
FahrenheitCelsius: Refactoring tests to use Parameters with JUnitParameters.