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
Looks like I'm mistaken, they do only use `staging` and `production`. I guess the only reason I would still suggest a `development` stage is for parity with rails environments. Having a development server to deploy to isn't unheard of either.