Bring RSpec current with rails 5 beta 3

Biggest issue here is a regression introduced in the rails controller
testing gem which forces us to do a require of
`action_controller/metal/rendering` in order to not give a NameError
when booting our test app.

Author: Sam Phippen

.travis.yml

@@ -58,11 +58,11 @@ matrix:
     - rvm: 2.2.2
       env: RAILS_VERSION=master
     - rvm: 2.2.2
-      env: RAILS_VERSION=5.0.0.beta2
+      env: RAILS_VERSION=5.0.0.beta3
     - rvm: 2.3.0
       env: RAILS_VERSION=master
     - rvm: 2.3.0
-      env: RAILS_VERSION=5.0.0.beta2
+      env: RAILS_VERSION=5.0.0.beta3
   exclude:
     # 3.0.x is not supported on MRI 2.0+
     - rvm: 2.0.0

lib/rspec/rails/configuration.rb

@@ -1,3 +1,5 @@
+require "action_controller/metal/rendering"
+
 module RSpec
   module Rails
     # Fake class to document RSpec Rails configuration options. In practice,