THRIFT-3176 ruby: Union incorrectly implements ==

Patch: István Karaszi
diff --git a/lib/rb/spec/union_spec.rb b/lib/rb/spec/union_spec.rb
index dd84906..a427090 100644
--- a/lib/rb/spec/union_spec.rb
+++ b/lib/rb/spec/union_spec.rb
@@ -53,6 +53,11 @@
       union.should_not == nil
     end
 
+    it "should not be equal with an empty String" do
+      union = SpecNamespace::My_union.new
+      union.should_not == ''
+    end
+
     it "should not equate two different unions, i32 vs. string" do
       union = SpecNamespace::My_union.new(:integer32, 25)
       other_union = SpecNamespace::My_union.new(:some_characters, "blah!")