Add Selenium support file for specs and include headless for Vagrant

Signed-off-by: Sebastian Serth <Sebastian.Serth@student.hpi.de>

Gemfile

@@ -66,12 +66,13 @@ end
 group :test do
   gem 'autotest-rails'
   gem 'capybara'
+  gem 'capybara-selenium'
+  gem 'headless'
   gem 'codeclimate-test-reporter', require: false
   gem 'database_cleaner'
   gem 'nyan-cat-formatter'
   gem 'rake'
   gem 'rspec-autotest'
   gem 'rspec-rails'
-  gem 'selenium-webdriver'
   gem 'simplecov', require: false
 end