Encapsulate whole code of app.rake into Tachikoma::Application class
require tachikoma/application from rake task file
Enable to use `mkdir_p`, `rm_rf` and `sh` from Tachikoma::Application
Define blank tasks for backward compatibility
Enable to choose build strategy
Add spec for Tachikoma::Application
Merge pull request #42 from sanemat/refactor_object_oriented

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