Gemfile in serf-0.11.0 vs Gemfile in serf-0.12.0

@@ -24,6 +24,7 @@
   gem 'rb-fsevent', require: false
   gem 'rb-fchange', require: false
 
   # Required by our Specs
   gem 'json-schema'
+  gem 'yell'
 end