Merge pull request ruby-rdf#83 from davidrupp/patch-2

Fix example code

Author: gkellogg

README.md

@@ -73,15 +73,15 @@ This is a [Ruby][] implementation of a [SPARQL][] client for [RDF.rb][].
     data = RDF::Graph.new do |graph|
       graph << [RDF::URI('http://example.org/jhacker'), RDF::Vocab::FOAF.name, "J. Random Hacker"]
     end
-    insert_data(data)
+    sparql.insert_data(data)
 
 ### Deleting data from a graph
 
     # DELETE DATA { <http://example.org/jhacker> <http://xmlns.com/foaf/0.1/name> "J. Random Hacker" .}
     data = RDF::Graph.new do |graph|
       graph << [RDF::URI('http://example.org/jhacker'), RDF::Vocab::FOAF.name, "J. Random Hacker"]
     end
-    delete_data(data)
+    sparql.delete_data(data)
 
 ## Documentation