DigitalOcean API Change (Sizes vs. Size Slugs)

DigitalOcean recently changed their API to stop including a nested version of the size object with droplets, and instead include the slug.

https://developers.digitalocean.com/changelog/api-v2/change-size-to-size-slug/

Here are some changes to work with this, however, I'd like some feedback as to where to properly fetch the list of sizes.