Leverage Rust's Traits to create a more dynamic API

[ajmwagar]

It would be awesome if stego could use traits to allow for custom encodable/decodable (source) datatypes along with custom host types.

I'm thinking an API similar to the following:

• Source trait is for encodable/decodable (hidden) data types.
• Host trait is for host files, like images/video/audio files that seem inconspicuous.

We could change the current LSBStego implementation to take in two type definitions. A Host and a Source then the LSBStego is the glue between the Source / Host.