modified from_xml to read thesaurus title in the form title, version
implemented inspire to_xsd function
added more from_xml tests and fixed error when reading wrong thesaurus name in from_xml
Merged with smanousopoulos/master (INSPIRE XSDs, tests)
Renamed tests for INSPIRE XML serializers
Reviewed INSPIRE XML serializers (to_xsd()). Must fix XSD paths.
Rewrote key-tuple serializer (accepts a prefix)
Minor fix at key-tuple serializer (accept non-empty prefix)
Fixed #37
Added several opts to schema flattening methods
Implemented #38 (field-level input serializers)
Round off #38 (support options for {to/from}_dict)
Refactored leaf field serializers
Replaced :input by :default serializers (forgiving loads method)
Merged with master