* Enable computation of the expiration date of the BSP file(s) on disk (requires to install the local repository using the [dev] option / See README for more information).
* Added a test to check if the current files are about to expire (45 days from now). Travis CI would run a monthly job and eventually report when it has failed, so actions can be done to refresh the files and "unbreak" the library.
* This project includes minimal data files required by the [Python Skyfield library](https://rhodesmill.org/skyfield/): `de421.bsp`, `deltat.data`, `deltat.preds` and `Leap_Second.dat`,
* It provides a small Python script to download the files from their respective source,
* This script eventually checks if some of the files are expired and skips them (by default),
* Usage documentation is included in the `README.md` file.
* This project code is released under the terms of the MIT License.