First major

This is the first major release for php-deal/framework. We made some adjustments so that this package could now be used in production.

Changed:

• Dropped support of php < 7.1
• Validation of Contracts:
  • An invalid validated contract will no longer raise a DomainException
  • You will now receive a better exception message with which contract was violated with what parameters
• Minor performance improvement on how annotations where merged from inheritance
• Added .gitattributes to avoid littering your space with useless files

Internal changes:

• Introduces strict_types throughout the project
• Changed coding style to PSR-12
• Added phpstan for more code quality
• Added type hinting and return types throughout the project
  • This made it possible to idenfity some minor issues with unclear return types
  • Removed tests which tried to call methods with wrong argument types