io.py
  1. Rename afspc_mode to opsmode,
      take a/i as input instead of True/False
  2. Clarify which mean anomaly (no) is used,
      satrec.no variable renamed to satrec.no_kozai,
      internal updates to support name change
  3. Make more internal variables available available to satrec

propagation.py
  1. Rename afspc_mode to opsmode,
      take a/i as input instead of True/False
  2. Initialize whichconst variables internally once,
      make values accessible in satrec
  3. delete unused variables in initl

test.py
  1. Replace deprecated assertRaisesRegexp with assertRaisesRegex

Notes:
  - Confirmed SGP4-VER.TLE is still current
  - Confirmed unit tests pass with
     python -m unittest discover sgp4