Merge pull request #1790 from jwoillez/fix_setup_helpers_subprocess

One more subprocess fix.
Merge pull request #1792 from astrofrog/fix-import-related-bugs

Fixed imports and undefined variables
Merge pull request #1793 from mdboom/vo/undefined-variable

Fix undefined variable problem in io.votable
Merge pull request #1795 from astrofrog/fix-fits-masking

Strange mask values for FITS table
Merge pull request #1788 from embray/fix-system-cfitsio

Fix bug when building with --use-system-cfitsio and CFITSIO < 3.35
Merge pull request #1707 from eteq/unit-formats-doc-clarification

Changed some of the wording in units docs to clarify what "unit formats" is about
Merge pull request #1806 from mwcraig/patch-3

Add upgrade instructions for anaconda users
Merge pull request #1810 from adonath/Fix_for_#1804

Fix for #1804
Reset the changelog to unreleaed for 0.3