species v0.2.1

• Faster runtime of FitModel by resampling the wavelengths only once prior to the sampling.
• Added the interpolate_grid function in FitModel.
• Refactoring of several ReadModel functions to make them independent of the model name.
• Additional keyword arguments in add_model to restrict the wavelength and temperature range of petitCODE and DRIFT-PHOENIX spectra.
• Updated tutorials and documentation.