Update to rocket v5

[Jackbaude]

I am having to use some async features for some other parts of my code, things that Rocket only supports in version 5.0. The version is currently not released but It would be nice to have a branch of this that started adapting version 5.0 since eventually it will be the release. A lot has changed so far.

edit: im not sure how active this is but im just putting this here if it still is

[svenstaro]

Hey, as it happens, I'm currently actually working with Rocket 0.5 so I'm definitely planning to update this repo.

[Jackbaude]

Great! I think some of the biggest changes that I have seen is the use of the Figment crate instead of the Config module