Change to common argument order in AngularSeparation
add test for AngularSeparation behavior
add exception module to utils
added warning for swaping lat/lon in AngularSeparation initializer
Added backwards incompatible changes section to What's New
Changed units-checking to work on real first argument
Consistent lon, lat for AngularSeparation

In the recent renaming a bug was introduced for a special case
(degree to radian conversion wasn't done).
This is now fixed and covered by a few more unit test inputs.
Fixed "shortcut" for when only leading parameter of AngularSeparation is non-0
Support letting the second, third, and fourth args of AngularSeparation be None
Merge pull request #3 from eteq/cdeil-angsep-fixinit

fix for AngularSeparation initializer oddities
Merge pull request #902 from cdeil/AngularSeparation with manual merge