Update website (e.g. replace infos about Atoum)

[k00ni]

Is there a way we can update content of the website pdfparser.org?

I am asking, because it contains outdated information, like https://www.pdfparser.org/documentation?utm_source=GitHub&utm_medium=documentation&utm_campaign=GitHub

@smalot

TODOs:

• [ ] Update Infos about test environment (Atoum => PHPUnit)
• [ ] update about minimum PHP version

[j0k3r]

We should also update the minimum version of PHP

[k00ni]

We should add further TODOs to the list on my initial post.