Allow specifying properties to avoid serializing before actually serializing.

[nilportugues]

Introduction of this feature will mean a big performance boost as it will deal with less information. Considering the process is already fast, it's good news.

This would mean passing an hash map, having as key a FQN class as string identifier and an array holding the names of the properties to be ignored.

[nilportugues]

API changes:

Concerning the hash Map, a proper object containing the logic should be passed, instead of an array.

$map = new SerializerMap();
$map->add("FQCN", ["property1", "property2"]);