[for discussion] move default localStorage location under $HOME

i ran into a problem when trying out your cash project. With my nodejs/npm setup, global installs require sudo: `sudo npm i -g cash`

however, because of that, cash doesn't have permissions to write to its own localstorage directory:

``` bash
$ cash
fs.js:794
return binding.mkdir(pathModule._makeLong(path),
^

Error: EACCES: permission denied, mkdir '/Users/tenaciousmv/npm/lib/node_modules/cash/node_modules/vorpal/dist/.local_storage'
```

obviously i don't want to run cash with sudo :)

isn't it more typical to put this kind of storage in ~/.vorpal or ~/.cash or somewhere else under `$HOME`?