Dependency Updates, Modernize Rust Version + Misc Enhancements

[bonedaddy]

Overview

Includes a number of changes that modernize the rust version in use, upgrades all dependencies, and uses better error handling:

• Rust edition change to 2021
• All dependencies updated to latest available version except nom (explained later)
• Remove the usage of failure and failure_derive, replacing them with anyhow and thiserror
• Applied formatting and linting
• Makes the visibility of the various B32 and B64 encoding types public, as they are needed by third-party crates
• Updates the crate version from to 0.2.0

Nom Upgrade Issues

Between version 6.0.0 and 7.0.0 of nom, the overall API of the library was significantly changed, such that the current nom parsers are no longer valid and need to be rewritten. Given that it represents a fairly significant logic change, I've left that out of this PR.