This is a tracking issue to document design and implementation of a verifier system for Rust Flatbuffers. I'm thinking that we can clone the logic from the C++ codebase.

The benefit is twofold:

1. Verifiers let users check if data is valid, thereby providing a security check for unknown data.
2. If a buffer is verified, we can justify using more unsafe pointer access in Rust, thereby removing bounds checking.

Anyone have thoughts on this? @aardappel