Update dependencies and Rust target version

Summary:
Bump libraries. That fixes an issue where ring crate wasn't provided anymore.

Adhere to rust 1.57: fix legacy_derive_helpers warning

Adhere to Rocket 0.4 and Limiting Factor 0.6+ code conventions:
use directly Status replies for 4xx and 5xx HTTP statuses.

Test Plan: cargo build

Reviewers: dereckson

Reviewed By: dereckson

Differential Revision: https://devcentral.nasqueron.org/D2429