Merge pull request #85 from activeadmin-plugins/fix_travis

fix travis build

Author: Fivell

Gemfile

@@ -3,6 +3,7 @@ source 'https://rubygems.org'
 # Specify your gem's dependencies in active_admin_importable.gemspec
 gemspec
 group :test do
+  gem 'sprockets-rails', '2.3.3'
   gem 'rails',  '4.2.0'
   gem 'rspec-rails'
   gem 'activeadmin', github: 'activeadmin'  , ref: 'd787029e5523be2eb2ed99816eb0cecca2b72862'