Octopress 3.0 Plugin & Theme Scaffold Logic

Tasks:

- [x] Setup commander-based command in `bin/octopress`.
- [x] Setup command structure in `lib/octopress`
- [x] Write logic to scaffold a new plugin's directories
- [x] Write logic to scaffold a new plugin's Rakefile
- [x] Write logic to scaffold a new plugin's Gemfile
- [ ] Write logic to scaffold a new plugin's integration with Octopress