Changes for swiftbat_python

v 0.1.5 2025-05-16

Moved all conditions for the calculation of the exposure to be inside batExposure
Made all returned values of batExposure be float values (both the area exposure and the cos(theta))
Modified simbadlocation to be able to access table RA/Dec values based on lowercase or uppercase headers, which changes with different versions of astroquery
Use https to access heasarc.
Update TLEs less frequently (10 days is adequate for source visibility).

Started CHANGES.md file
Replace pyephem with skyfield
- pyephem is no longer supported
Pointing history replaced screen-scraping with swifttool database access
- Appeared as DOS on the scraped website when I ran too often
General decrufting
- reformatted with black
- Code still suffers from being the first Python I ever wrote, on python2.6
- Some (but not much) type hinting)
Requirements updated:
- Python >= 3.9
- astropy >= 5
- skyfield >= 1.4