re-add postal signatures to outgoing http requests

lib/postal/http.rb

@@ -38,8 +38,8 @@ module Postal
       end
 
       if options[:sign]
-        #signature = EncryptoSigno.sign(Postal.signing_key, request.body.to_s).gsub("\n", '')
-        #request.add_field 'X-Postal-Signature', signature
+        signature = EncryptoSigno.sign(Postal.signing_key, request.body.to_s).gsub("\n", '')
+        request.add_field 'X-Postal-Signature', signature
       end
 
       request['User-Agent'] = options[:user_agent] || "Postal/#{Postal.version}"