[ANN] New Version of AstroTime.jl v0.4.0

Hey folks,

There is a new version of AstroTime.jl which is sufficiently different to warrant a new announcement here :tada:

While the user-facing API has remained fairly stable, one of the most important features, transformation between different time scales, has been completely re-engineered.

In the past we assumed that all time scales can be based on International Atomic Time (TAI) one way or another. Essentially all epochs (dates) were assumed to be absolute. This assumption does not hold in reality. Space-time is relative (thanks Einstein :stuck_out_tongue_winking_eye:).

Taking this into account, we re-implemented time scale transformations to be relative (https://github.com/JuliaAstro/AstroTime.jl/pull/48). In the process, we also changed the representation of epochs to be less abusive of Juliaβ€˜s type system and improved consistency of the API.

TL;DR: New version, better model of reality, improved API. Enjoy :tada::smile: