Add case-insensitive test of delete

spec/lib/msf/core/data_store_spec.rb

@@ -25,8 +25,9 @@ shared_examples "datastore" do
     end
   end
   context "#delete" do
-    it "should delete the specified key" do
+    it "should delete the specified case-insensitive key" do
       subject.delete("foo").should == "bar"
+      subject.delete("Fizz").should == "buzz"
     end
   end
 end