Rust client 1.4 feature parity

[PeterShinners]

The rust client library now has more parity with the other languages. The stream() call is operational, along with a guaranteed failure fallback image, and other small cleanups.
https://crates.io/crates/thumbrella-client

[PeterShinners]

It's still a little behind on having a persistent cache option. I mainly wasn't sure what the right third party dependencies and format should be. Likely sqlite which is great for just about everything. But I also wasn't sure on decisions like a forced or optional dependency. So punting for now.