Modules installer

This is a simple modules installer (can't handle multiple files, or requirements yet)

It connects to http://jaspermoduleshub.herokuapp.com/

I added a `walk_packages` on `brain.py` so that modules can be installed in subfolders.
Why not do:
```Python
MODULES_URL = 'http://jaspermoduleshub.herokuapp.com/plugins/%s.json'
def _module_url(module):
    return MODULES_URL % urllib.quote(module)
```