v2.3.0

Version 2.3

• Brings a new transit model, pytransit.OblateStarModel for modelling transits over gravity-darkened rapidly rotating stars (Barnes 2009),
• Renames pytransit.SwiftModel to pytransit.RoadRunnerModel,
• Fixes bugs introduced in 2.2 by moving to use the Taylor series expansion to calculate the projected planet-star distances.