rb: Use File.dirname(__FILE__) in generated requires [THRIFT-57]

This means you no longer have to put the gen-rb folder in $:

Author: Kevin Ballard <kevin@rapleaf.com>


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@671963 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/rb/spec/serializer_spec.rb b/lib/rb/spec/serializer_spec.rb
index 57e20ab..fe5a86a 100644
--- a/lib/rb/spec/serializer_spec.rb
+++ b/lib/rb/spec/serializer_spec.rb
@@ -1,6 +1,6 @@
 require File.dirname(__FILE__) + '/spec_helper'
 require 'thrift/serializer'
-require 'ThriftSpec_types'
+require File.dirname(__FILE__) + '/gen-rb/ThriftSpec_types'
 
 class ThriftSerializerSpec < Spec::ExampleGroup
   include Thrift