Persist install selection

:fork_and_knife: 

When a signed in user clicks the install instructions for a cookbook, persist their selection on their account.

todo:

- [ ] update the installs view to be less nutso
- [x] get the feature spec passing

Trello card: https://trello.com/c/l7YoGfzK
It might be a bit more explicit if rather than keying off of this if we added a class to the install tab links if there is a current user. Like:

```erb
<a href="#berkshelf" class="button tiny secondary <%= if current_user? 'persist-install-method' %>'">Bershelf</a>
```

Then we can get rid of this conditional and just make the event binding.

```javascript
$(".persist-install-method").click(function() {
});
```