Merge remote-tracking branch 'origin/master'

# Conflicts:
#	composer.json
#	composer.lock
#	src/Exceptions/DecodeMessageFailed.php
#	src/Exceptions/DenormalizeFailed.php
#	src/Exceptions/EncodeMessageFailed.php
#	src/Exceptions/NormalizationFailed.php
#	src/Exceptions/SerializationFailed.php
#	src/Exceptions/SerializerExceptionMarker.php
#	src/Exceptions/UnserializeFailed.php
#	src/JsonSerializer.php
#	src/MessageDecoder.php
#	src/MessageEncoder.php
#	src/Serializer.php
#	src/Symfony/Extensions/EmptyDataDenormalizer.php
#	src/Symfony/Extensions/EmptyDataNormalizer.php
#	src/Symfony/Extensions/PropertyNameConverter.php
#	src/Symfony/Extensions/PropertyNormalizerWrapper.php
#	src/Symfony/SymfonyMessageSerializer.php
#	tests/Stubs/Author.php
#	tests/Stubs/ClassWithPrivateConstructor.php
#	tests/Stubs/EmptyClassWithPrivateConstructor.php
#	tests/Stubs/TestMessage.php
#	tests/Stubs/WithDateTimeField.php
#	tests/Stubs/WithNullableObjectArgument.php
#	tests/Symfony/SymfonyMessageSerializerTest.php

Author: mmasiukevich