Update README.md
fixes a missing reference to rdflib when using Namespace()
@@ -52,7 +52,7 @@ exist). New Namespaces can also be defined:
```python
-dbpedia=Namespace('http://dbpedia.org/ontology/')
+dbpedia=rdflib.Namespace('http://dbpedia.org/ontology/')
abstracts=list(x for x in g.objects(semweb, dbpedia['abstract']) if x.language=='en')
```
