(v3) Renamed task list

This patch is implemented based on the discussion in capistrano/rails#3.

Changes:

- rename tasks with descriptive names (see the new runlist below)
- add new task hooks: updated, reverting, reverted, finishing_rollback
- invoke `deploy:check` in `deploy:starting`
- invoke `deploy:restart` in `deploy:publishing`
- invoke `deploy:revert_release` (set previous release timestamp) in `deploy:reverting`
- move `deploy:rollback` to `framework.rake`

New runlist:

```
deploy
--
starting
started
updating
updated
publishing
published
finishing
finished

rollback
---
starting
started
reverting
reverted
publishing
published
finishing_rollback
finished
```