extended execution environments by a default file type that is used as the default for associated exercises' files

db/migrate/20150310150712_add_file_type_id_to_execution_environments.rb

@@ -0,0 +1,5 @@
+class AddFileTypeIdToExecutionEnvironments < ActiveRecord::Migration
+  def change
+    add_reference :execution_environments, :file_type
+  end
+end