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.
You should use `jasperpath.PLUGIN_PATH`. This won't work it's executed from outside the client folder, e.g:
```bash
cd /
/home/pi/jasper/client/modinstaller.py --install foo
```

In this case, it will try to create `/modules/foo` (in the root fs).