Version 3.7.5.3

Tag v3.7.5.2 (second try)

Changed version numbers to 3.7.5.1 in index.html; now ready for release.

Updated version to 3.7.4.1.

Upped the version to 3.7.3.4 in preparation for release.

Last tweaks made while releasing "ephem" to PyPI for the first time.

Got versions positioned for 3.7.3.2 release. The setup.py and the

documentation build scripts now consult ephem/__init__.py for the
current version rather than requiring several copies of the value to be
scattered across the codebase.

Upgraded all version numbers to 3.7.3.1.

Removed redundancy.