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
Neither of these *need* to be set before requiring the `mina/multistage` file, they only should be set before requiring the file if you want to override the defaults. I think we should clarify this point a bit more.