Using Thor for CLI/scaffold generator. Fancy!

Thor::Group/Thor::Actions handles almost all of the common generator tasks like file copying, overwrite prompting, template parsing (by naming a template file with *.tt), etc.. It also handles CLI tasks like usage info, option parsing, required options, and so on. This should also make any future CLI stuff easy to add.

- Replaced scaffold generator with Thor::Group/Thor::Actions generator
- bin/napa now uses Napa::CLI (Thor)
- Moved lib/generators into lib/napa/generators since they are namespaced under Napa
- Added app_name to hello_api.rb and config.ru templates, no need to manually replace 'HelloWorldService' anymore since it uses the app_name

![screen shot 2013-12-28 at 10 34 06 am](https://f.cloud.github.com/assets/3131496/1818085/ebbba5d0-6fdd-11e3-8137-f5e247644383.png)

![screen shot 2013-12-28 at 10 31 54 am](https://f.cloud.github.com/assets/3131496/1818078/a5a8e288-6fdd-11e3-8541-45b8529a16bc.png)

![screen shot 2013-12-28 at 10 33 14 am](https://f.cloud.github.com/assets/3131496/1818081/cb9d963c-6fdd-11e3-92be-8843ddeca92f.png)