WIP: Testing with pg in travis... Add missing rake.

Gemfile

@@ -49,6 +49,7 @@ group :test do
   gem 'selenium-webdriver'
   # Easy installation and use of web drivers to run system tests with browsers
   gem 'webdrivers'
+  gem 'rake'
 end
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem