Jdcal

Remove testing for Python 2.6 and 3.3.
Added testing for Python 3.7. For current Python versions tested
see travis.yml.

Removed unused function `fpart`.

Universal wheel distribution.
Test to compare gcal2jd with astropy._erfa.cal2jd.
Add more Python versions on Travis.

Use setuptools instead of distutils. This enables package managers to
create Python wheels.

See PR 7.

No change in functionalities.

Added test_jdcal.py; removed test functions from jdcal.py.

Added CHANGELOG.txt.

Minor changes to README.rst.

This version has exactly the same code as in jdcal 1.0, except the
tar file has LICENSE.txt in it.

See issue 5 (https://github.com/phn/jdcal/issues/5) for why this version
was created.