Release 4.0.0
Includes the following merges:
- PR #52: Unified documentation style
- PR #50: Shiny workflow update
- PR #49: Shiny workflow update
- PR #48: Shiny
- PR #47: Disable automatic astropy.iers downloads
- PR #46: Change so date like 2020:001 is midnight not noon
- PR #45: Flake8
- PR #42: Support CxoTime in DateTime and modernize
- PR #43: Migrate pydocs sphinx docs to project
- PR #44: Version for shiny
- PR #40: Allow setup.py --version to work without Cython