Add retry on travis to reduce random failures

closes #7932

lib/tasks/cucumber.rake

@@ -20,6 +20,7 @@ begin
       t.binary = vendored_cucumber_bin # If nil, the gem's binary is used.
       t.fork = true # You may get faster startup if you set this to false
       t.profile = 'default'
+      t.cucumber_opts = %w[--retry 3]
     end
 
     Cucumber::Rake::Task.new({:wip => 'db:test:prepare'}, 'Run features that are being worked on') do |t|