Test more Python versions on travis.
Add more Python versions in classifiers in setup.py.
Change version number in jdcal.py.
Add test to compare gcal2jd with astropy._erfa.cal2jd.
Add universal wheel support by adding information to "setup.cfg".
Many editors clean up trailing white space on save. By removing it all
in one go, it helps keep future diffs cleaner by avoiding spurious white
space changes on unrelated lines.
1) Use setuptools instead of distutils.
I will continue non-wheel on pypi since I am not familiar with
wheels, and can't spend time on it if this breaks someone's
2) Made entry in changelog.
Minor changes in README.rst.