10.3.0: XP 12 compatibility

• Made compatible with XP 12 - @thekid

10.2.0: Collection parts

• Merged PR #57: Retrieve collection parts - @thekid
• Merged PR #55: Migrate test suite - @thekid

10.1.0: Single operation

• Introduce dedicated util.data.NoSuchElement exception. It's thrown
  from Optional::get() if no element is present instead of the generic
  util.NoSuchElementException. For BC reasons, it extends the latter.
  (@thekid)
• Implemented PR #54: Implement Sequence::single() - which is similar
  to first() but raises an exception if there are more than 1 element
  in the sequence.
  (@thekid)

10.0.0: Drop XP 9, add XP 11

• Implemented xp-framework/rfc#341, dropping compatibility with XP 9
  (@thekid)

9.3.0: Zip intermediate

• Merged PR #53: Implement Sequence::zip() intermediate operation
  (@thekid)

9.2.0: Intermediate NOOPs

• Merged PR #52: Allow NULL for Sequence methods peek(), map(), filter(),
  skip(), limit() as well as Optional methods map() and filter()
  (@thekid)

9.1.1: PHP 8.1 compatibility

• Fixed PHP 8.1 compatibility for Traversable subtypes - @thekid

9.1.0: Collections library compatibility

• Added compatibility with xp-framework/collections version 10.0.0
  (@thekid)

9.0.1: Test code refactoring

• Simplified test code, making use of anonymous classes, the RuntimeVersion
  action and Assert::throws(), see pull request #50
  (@thekid)

9.0.0: Drop PHP 5 support

• Implemented xp-framework/rfc#334: Drop PHP 5.6. The minimum required
  PHP version is now 7.0.0!
  (@thekid)