Rename eos utils to piecewise polytrope
- renamed eos_utils to piecewise polytrope
- updated the
combine_GW170817_and_GW190425.pyexample - added the option to calculate mass-radius and pressure-density posteriors
- added the option to calculate mass-radius and pressure-density confidence intervals
- added constant speed of sound parametrization of the EoS (css)
- improved lambda-mass interpolation