Refactoring: introducing more object-oriented way to organise code codes

Monolithic big rake task is hard to maintain in future, so slim-up app.rake and move whole code into Tachikoma::Application class.
This brings a few benefits now, but plain-old ruby object is good for testing (more test gives us more maintainability)

I also add two tasks: tachikoma:run_bundle and tachikoma:run_carton.
Existent task chain works for backward compatibility, too.