Structuring development (issue #7)

Here is my suggestion about structuring development as I explained in issue #7.
* I removed ressources folder.
* I added bower and composer json files.
* I edited CONTRIBUTING.md accordingly fixing some informations while doing so.

To install dependencies developer will need to get his clone then in the working directory just issue:
```bash
composer install
bower install
```
This wil also limit files in the repo. :wink:
## TODO
* gruntfile
* further explanation on CONTRIBUTING.md