SGP4 propagator enabled
copyright changed to 2014
python exposition of sgp4 classes
SGP4 test added
Fix for missing clock_gettime on Max OS X. Fix for tests if SGP4 is not enabled.
Merge pull request #2 from dhennes/master

Fix for missing clock_gettime on Max OS X. Fix for tests if SGP4 is not enabled.
Merge pull request #10 from darioizzo/master

update on sgp4