Fix / update crate docs (#200)

## What?

- Removes obsolete lifetime mentions from crate docs.
- Adds a `docs.rs` badge to the typing crate readme.

## Why?

To maintain docs quality.

Merge pull request #89 from slowli/prepare-release

Prepare v0.3.0 release

Merge pull request #51 from slowli/prepare-release

Prepare release v0.2.0

Mark release v0.2.0-beta.1 in changelogs

Merge pull request #2 from slowli/separate-eval-crate

Separate eval crate