Test TAEG

Your colleague began to write his implementation for an APR calculator (TAEG). Now he is ill and you have to finish his work.

Some info regarding the business domain you can find here:

• Italian: https://it.wikipedia.org/wiki/Indice_sintetico_di_costo
• English: https://en.wikipedia.org/wiki/Annual_percentage_rate

TODO

1. Run composer install in the directory
2. Run phpunit right after
3. Implement the methods so that these tests can pass
4. Refact the code a bit because our server runs with PHP 7.0 installed