Add Apache Maven's support to the project

You have to add Apache Maven to your project. This tool will help you build your project (create a jar archive), to version your project and run tests (and so on).

Maven is a tool. You install it at your system and you can check the availability of maven at your system using next command in the command line:
```
mvn --version
```
If it doesn't exist you can install it (or on your Intellij Idea it's installed by default).

Using Maven you can install external libraries and it will be really helpful in the future.