Use version variable for tag number

@@ -7,7 +7,7 @@ Pod::Spec.new do |s|
   s.author   = { 'Jonas Budelmann' => 'jonas.budelmann@gmail.com' }
   s.social_media_url = "http://twitter.com/cloudkite"
 
-  s.source   = { :git => 'https://github.com/cloudkite/Masonry.git', :tag => 'v0.6.2' }
+  s.source   = { :git => 'https://github.com/cloudkite/Masonry.git', :tag => "v#{s.version}" }
 
   s.description = %{
     Masonry is a light-weight layout framework which wraps AutoLayout with a nicer syntax.