Fix #2418: Fix crash in smart resolver when the resolution doesn't work.
Added some entries for 0.4 what’s new.
Merge pull request #2560 from astrofrog/whatsnew-0.4

Added some entries for 0.4 what’s new
Updated supported Python versions
Merge pull request #2591 from mdboom/docs/smart-resolver-fix-crash

Fix #2418: Fix crash in smart resolver when the resolution doesn't work.
Updated CHANGES.rst for #2591
updated to latest astropy-helpers and ah_bootstrap