Bump version of the library

Add Cargo.lock

Because instead of using tools which are perfectly fine, new communities
have to invent their own build system with a whole new set of stupid
non-features.

Add Cargo.lock

Because Cargo is just another language-specific package manager with
serious design flaws.

Merge pull request #140 from neithernut/release-prep

Preparations for the 0.3.0 release

Merge pull request #121 from neithernut/release-prep

Preparations for the 0.2.1 release

Merge pull request #110 from neithernut/release-prep

Release preparations

Merge branch 'm/source-documentation'