safe clean of an object prior to serialization

 This module clean up (fill with zero byte) an object before sending
 to serialisation, thus avoiding to serialize private data.
 This module supports generalisation by allowing ones to specify
 filter function, that support whitelisting.
 .
 Clearing data before serialization is critical from a security
 point of view in order to avoid leaking information.
 .
 Node.js is an event-based server-side JavaScript engine