Collections Abstraction library

• Require PHP 7.1+
• Drop HHVM support

• Require PHP 5.6+
• Add ArrayCollection::createFrom()
• Support non-camel-case naming
• Comparison START_WITH, END_WITH
• Comparison MEMBER_OF
• Add Contributing guide

• Explicit casting of first and max results in criteria API
• Keep keys when using ArrayCollection#matching() with sorting
• Made AbstractLazyCollection#$initialized protected for extensibility

• Add a new AbstractLazyCollection

• Deprecated Comparison::IS, because it's only there for SQL semantics. These are fixed in the ORM instead.

• Add Comparison::CONTAINS to perform partial string matches:

    $criteria->andWhere($criteria->expr()->contains('property', 'Foo'));