4.1.0: Merge pull request #1 from vlada-dudr/master

PHP8 compatibility

PHP ^7.1 || ^7.2

• Minimum required PHP version set to ^7.1 || ^7.2
• Run PHPUnit on PHP 7.1 and 7.2
• Updated PHPUnit ^7.1
• Added strict typing
• Added return types
• General cleanup

3.1.1

type hinting

3.1.0

updated dependencies and prepared release 3.1.0 with better API