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.
Seems a bit strang to me. I'd prefer:
```Python
if args.install:
    installer = ModuleInstaller(install_locations=[jasperpath.PLUGIN_PATH, os.path.join(jasperpath.CONFIG_PATH, 'plugins')])
    for module in args.install:
        installer.install(module)
```

You then iterate through the `install_locations` list and check if the directory is writable (with `os.access()`) and raise an error if none of them is.