Use ActionControlller::Base instead of ApplicationController

After a controller is changed, Rails reloads the controller files. The methods included by ``register_apis`` are lost after the reload. Rails then throws a 
``undefined method `swagger_controller' for YoloSwagController:Class``. The issue was also reported in #27

This PR changs the base controller to ``ActionController::Base`` so the included methods are not lost and devs can happily change their controllers for many days to come!