Downgrade sentry-raven to 2.11.x

The latest version 2.13.0 has changed the error structure, so
`error_handling_spec.rb` has a failure.
Until we figure out the proper update, we stay with the known
version.

Author: BanzaiMan

Gemfile

@@ -22,7 +22,7 @@ gem 'simple_states',   '1.0.2'
 
 gem 'active_model_serializers'
 gem 'unicorn'
-gem 'sentry-raven'
+gem 'sentry-raven', '~> 2.11.3'
 gem 'yard-sinatra',    git: 'https://github.com/rkh/yard-sinatra'
 gem 'rack', '>= 2.1.4'
 gem 'rack-contrib'

Gemfile.lock

@@ -361,7 +361,7 @@ GEM
     ruby2_keywords (0.0.2)
     ruby_dep (1.5.0)
     safe_yaml (1.0.5)
-    sentry-raven (2.13.0)
+    sentry-raven (2.11.3)
       faraday (>= 0.7.6, < 1.0)
     sidekiq (5.2.9)
       connection_pool (~> 2.2, >= 2.2.2)
@@ -481,7 +481,7 @@ DEPENDENCIES
   rspec
   rspec-its
   s3!
-  sentry-raven
+  sentry-raven (~> 2.11.3)
   sidekiq
   simple_states (= 1.0.2)
   simplecov