Test suite: Remove load path modifications

Adding ../ext to the load path causes the tests to load an extension
linked to the wrong Ruby version when building for multiple Ruby
versions. This (obviously) causes the interpreter to crash.

Index: ruby-patron/spec/spec_helper.rb
===================================================================
--- ruby-patron.orig/spec/spec_helper.rb	2014-03-05 20:44:17.814566313 +0100
+++ ruby-patron/spec/spec_helper.rb	2014-03-05 20:47:25.190033067 +0100
@@ -23,8 +23,6 @@
 ## -------------------------------------------------------------------
 require 'rspec'
 
-$:.unshift(File.dirname(__FILE__) + '/../lib')
-$:.unshift(File.dirname(__FILE__) + '/../ext')
 require 'patron'
 
 Dir['./spec/support/**/*.rb'].each { |fn| require fn }
