Implement __toString(), JsonSerializable, Serializable

[grimzy]

Implement __toString() on GitInfo class to be able to echo $gitInfo and get the string representation of $gitInfo->getInfo().

(If needed) Implement JsonSerializable on GitInfo class to be able to json_encode($gitInfo) and get the JSON representation of $gitInfo->getInfo().

(If needed) Implement Serializable on GitInfo class to be able to $gitInfo->serialize() and get the serialized representation of $gitInfo->getInfo().