Bump version to 1.0.0

The breaking changes I'm working on are severe enough that this should
be considered 1.0.0. Folks are using it in production, so breaking
changes should come as a 2.0.0

Bump version to 0.6.1

Bump version to 0.6.0

Release version 0.5.4

Release version 0.5.3

Release version 0.5.2

Release version 0.5.1

Release version 0.5.0

Release version 0.4.1

Release version 0.4.0