v0.9.0

• Added PHP 8 support
• Dropped ext-tarantool support
• API changes:
  • Removed the final keyword from the Queue class
  • Added Queue::getClient()
  • Added private constructor to classes Options and States
  • Renamed Task::createFromTuple() to Task::fromTuple()
  • Removed TarantoolAdapter
• QA:
  • Refactored tests to use PHPUnit Extras
  • Added the PhpUnitCompat trait
  • Switched to travis-ci.com
  • Added Psalm configuration
  • Added Scrutinizer configuration