Add missing public API docstring.
added changelog entry for #1826

[ci skip]
added v0.4 what's new document and updated links
Adjusted for numpydoc convention
Add missing docstrings.
Add changes to io.fits
Fixed 26 out of the 36 (non-functioning-api)warnings in 'whatsnew' folder
Fixed broken API links
Fixed remaining issues
Made more improvements. Almost ready for merge.
Fixed broken links in 'vo' and 'wcs' modules.
Fixes the warnings during test runs.
Fixed broken links in time, and few in units module
Fixed 3 broken links.
Fixed a link in equivalencies.rst
added double tiks around "2010-01-01 00:00:00" and changed 'astropy' to 'Astropy'
Fix backtick error pointed out by @embray

[ci skip]
Fixed typos pointed out by @cdeil
Add __call__ to Sphinx API docs (fixes #1817)
Make `@deprecated` decorator work for classes.