initial structure of coordinates subpackage
Added coords_example.py

This file should be removed once the examples have been converted to the
testing framework
added coordinates modules
updated example for changes in gist
converted coords_example to tests
moved Angle import into individual tests
added coordinates documentation to doc index
to_string -> format
updated to new astropy.units
More work on core, updated several tests.
New work on core, etc.
More work on Angle, RA classes. Improved __eq__ on Angle.
Typos.
Work on RA, Angle operators, test code.
Added more tests, new conversion routines, to_string handling.
Typos, tabs.
Starting work on "Coordinates", expanded custom errors, bug fixes.
Further development on Coordinates.
More work on coordinates classes, new tests.
Updated tests, modifications based on feedback, fixed a few bugs.