Feature: Upgrade a Chef Omnibus Installation

Its a bit of a :frowning: to upgrade an already-bootstrapped node's Chef installation. You can use the [omnibus_updater](https://github.com/hw-cookbooks/omnibus_updater) cookbook, but it 
* doesn't support Windows MSI
* requires you to somehow (role, override, w/e) get it into your run-list.

The idea here is to add a new feature `upgrade_omnibus` which acts very similarly to the `uninstall_chef` functionality.

Basically, I've written a Bash and Batch version of the script that does a few things:
* Writes a recipe that uses some logic and remote_file to download the appropriate Omnibus file.
* Uses `chef-solo` or `chef-apply` to execute the above recipe.
* Install the Omnibus file.
* Cleanup

Ultimately, we'd have a pretty clean API that we can then implement somewhere else without having to worry about the top bullets:

```
ridley = Ridley.new(options)
ridley.node.update_omnibus("kylesmachine.foo.com", chef_version: "11.12.4")
```
 :construction:

I'm passing this forward to @ivey and am going to leave some comments about what I've written so far.