dunder 0.3.0

For tasks that can be started early and evaluated late. Typically one might want start multiple heavy tasks concurrent. This is already solvable with threads or the [reactor-pattern](http://rubyeventmachine.com/) but setting this up could be cumbersome or require direct interactions with threads ex. Dunder is a simple way of abstracting this: you simply pass a block to Dunder.load with the expected class as the argument