Add deploy:<stage> tasks & Deploy staging by default & Refactoring

* Add `deploy:<stage>` tasks
* Deploy staging with default `deploy` task
* Rename `multistage:create_stagefiles` -> `mutistage:init`
* Remove `config/deploy/development.rb` stage file
This must be added to the `config/deploy.rb` before `mina multistage:init` will work.