minor changes

spec/factories/file_type.rb

@@ -181,7 +181,7 @@ FactoryGirl.define do
     singleton_file_type
   end
 
-  %w(binary executable renderable).each do |attribute|
+  [:binary, :executable, :renderable].each do |attribute|
     trait(attribute) { send(attribute, true) }
   end
 

spec/factories/shared_traits.rb

@@ -1,5 +1,5 @@
 FactoryGirl.define do
-  %w(admin external_user teacher).each do |factory_name|
+  [:admin, :external_user, :teacher].each do |factory_name|
     trait :"created_by_#{factory_name}" do
       association :user, factory: factory_name
     end