Bump version to 3.2.1 and update changelog

CHANGELOG

@@ -1,6 +1,8 @@
-== Version 3.2.1 (Unreleased)
+== Version 3.2.1
 
 * Added CarrierService resource
+* Added optionally using threadsafe ActiveResource (see readme)
+* Fixed bug in validate_signature
 
 == Version 3.2.0
 

lib/shopify_api/version.rb

@@ -1,3 +1,3 @@
 module ShopifyAPI
-  VERSION = "3.2.0"
+  VERSION = "3.2.1"
 end