Better README, Grunt 0.4, Config file & new folder structure.

This PR includes lots of changes:

* Finished Grunt 0.4 migration
* add happy-plan.json configuration file (yes it's aweseome)
* remove shell call to fontcustom (use grunt-webfont instead)
* Better compass configuration (especially http_*_path for build)
* Rearrange folders structure.
* default task build (dev) before watch
* livereload ! (that's why grunt-contrib-watch has been replaced by grunt-regarde, ping me for more info about that if needed) - need [livereload browser extension](http://go.livereload.com/extensions) for now.

What do you think ?