Added accepts_nested_attributes_for on RDFNodes
[RDF][nested_attributes] dont attempt to set attributes for association if no attributes provided for that association
[RDF] refs #75 stabilizing nested_attributes behavior; .build() now accepts and sets attributes; created comparison operator for Nodes
[RDF] refs #75 RDF::Node.build and RDF::Node.attributes= support auto-building nodes from string values; Plus lots of test coverage.
Make sure active_support/core_ext/hash/except is required
RDF nested attributes handle default values with RDF.value predicate