serde_bser: Apache-2.0 license file missing from git repo and published crates

The `serde_bser` crate maintained as part of this project lists its license as `Apache-2.0` in its `Cargo.toml` file, but there's no license text for Apache-2.0 in the crate, and not in this entire repository, as far as I can tell.

The Apache-2.0 is one of the licenses which require redistributed sources to contain a copy of the license text, so it would be great if the serde_bser crate included it - currently, crates distributed via crates.io (or in Linux Distributions) don't satisfy this requirement of the project's license (because they cannot).