Json Api Common Laravel Package

1. added "merge" to resource collections
2. added "merge" to relationship collections
3. added "merge" to link collections

1. merged "added \Countable interface to collections"

1. ignore case match for simple collection keys
2. ad content type header as default for requests

Model changes:

1. renamed all occurrences of method "metaInformations" to "metaInformation"
2. renamed method ResourceInterface::getType() to ResourceInterface::type()
3. renamed method ResourceInterface::getId() to ResourceInterface::id()
4. renamed method RelationshipInterface::getType() to RelationshipInterface::type()
5. renamed method RelationshipInterface::getName() to RelationshipInterface::name()
6. renamed method LinkInterface::getType() to LinkInterface::type()
7. renamed method LinkInterface::getName() to LinkInterface::name()
8. renamed method ErrorInterface::getStatus() to LinkInterface::status()
9. renamed method ErrorInterface::getCode() to LinkInterface::code()
10. renamed method ErrorInterface::getTitle() to LinkInterface::title()
11. renamed method ErrorInterface::getDetail() to LinkInterface::detail()
12. added method "createLink" to LinkCollectionInterface
13. removed method "getType", which was only relevant for serializer, from DocumentInterface
14. added method "httpStatus" to DocumentInterface
15. added method "withHttpStatus" to DocumentInterface, to modify the status of a document
16. added method "shouldBeHandledAsCollection", which indicates if a document contains a collection or not, to DocumentInterface
17. added method "jsonApi", which contains information about the version, to DocumentInterface
18. added model class Document as default implementation of DocumentInterface
19. removed class AbstractDocument (use Document instead)
20. removed class ResourceDocument (use Document instead)
21. removed class ResourceCollectionDocument (use Document instead)
22. removed class RelationshipDocument (use Document instead)
23. removed class RelationshipCollectionDocument (use Document instead)
24. removed class ErrorDocument (use Document instead)
25. added interface JsonApiInterface for information about the used version in documents
26. added model class JsonApi as default implementation of JsonApiInterface for information about the used version in documents
27. added interface DocumentFactoryInterface and class DocumentFactory
28. added interface ResourceFactoryInterface and class ResourceFactory
29. added class ResourceFactoryRegistry
30. added interface RelationshipFactoryInterface and class RelationshipFactory
31. added interface FetchRequestInterface
32. added class FetchRequest
33. added interface JsonApiRequestInterface
34. added class JsonApiRequest
35. added interface SaveRequestInterface
36. added class RelationshipModificationRequest
37. added class SaveSingleResourceRequest

Serializer changes:

1. added argument "identifiersOnly" as second argument of DocumentSerializerInterface::serializeDocument
2. added the key "jsonapi" to output of Serializer::serializeDocument
3. added interface DocumentDeserializerInterface
4. added class Deserializer as default implementation of DocumentDeserializerInterface

new in 2.0.0

1. added JsonApiInterface and JsonApiTrait
2. added interface JsonApiAwareInterface and trait JsonApiAwareTrait

1. Request: define array properties default as empty array

1. merged "Fix relationships URL"
2. merged "Declare public constant for json api Content-Type"
3. fixed #11 ("CreatedResponse does not return document")