Added requirements file
Removed unnecessary requirements
Merge with updated original
Refactored a few tests to use pytest and fixtures
Merge remote-tracking branch 'upstream/master'
changing constant tau to TAU
completed refactoring tests, removing older tests
changing self.delta to epsilon and removing NOVASTests class
Merge branch 'feature/fixtured-tests'
Merge remote-tracking branch 'upstream/master' into keplerian_orbits
Added kepler's third law conversions
Added eccentric anomaly calculation