Prevent running the scheduler twice.

The rufus scheduler was being started twice since the refactoring of breaking out dashing into several modules. The cause of it is because the bin requires 'dashing', which in turn requires dashing/app which will create a new instance of the scheduler. Then, once thin boots up and loads the config.ru, it requires 'dashing' again, creating yet another instance of the scheduler. 

We could go ahead and only require 'dashing/app' inside the config.ru, but that would mess up previous people's config files. 

This is something to refactor in Dashing 2.0.