Updated nokogiri dependency

Author: brianmc

authorizenet.gemspec

@@ -14,7 +14,7 @@ Gem::Specification.new do |s|
   s.required_ruby_version     = '>= 1.9.3'
   s.required_rubygems_version = '>= 1.3.6'
 
-  s.add_runtime_dependency "nokogiri", ">= 1.6.4", "< 1.6.5"
+  s.add_runtime_dependency 'nokogiri', '~> 1.6', '>= 1.6.4'
   s.add_runtime_dependency "roxml", "= 3.3.1"
 
   s.add_development_dependency 'rake', '~> 0.8', '>= 0.8.7'