Major revisions to app generator, add permission, samples sub-generator

I made new version generator for chromeapp. What new things is

- Revision chromeapp:app generator
  - legacy permission code removed
  - permission sub-generator added
- permission sub-generator added
- google-chrome-samples sub-generator added
- coffee-script, compass task has been disabled in temporary

Please refer to new [readme.md](https://github.com/ragingwind/generator-chromeapp/blob/master/readme.md) for understanding

@addy I disabled coffee-script, compass tasks to reduce confusion of users. I'll that tasks put into next version of the generator. But until now, I could not found the way of using livereload with coffee-script and compass so clearly. as you know, 'webapp generator' can using intermediate path (.tmp) but chromeapp can't do it, all of generated files has be still under the source path. 

If you have any ideas? please let me know.