Minor improvements

Set default value of the $iri parameter of rdfInterface::DataFactory::defaultGraph($iri) to null.

Make Parser independent of DataFactory implementation

The rdfInterface\Parser class constructor takes the rdfInterface\DataFactory instance now allowing a parser to work with any rdfInterface\DataFactory implementation.

Serialize spelling made consistent

Previously there was a Serializer class with serialise() and serialiseStream() methods. Method names are serialize() and serializeStream() now.

Initial release

0.1.0

Syntax fixes in composer.json