species v0.5.3

• Support for BT-Dusty model spectra (add_model('bt-dusty'))
• Support for BT-Settl isochrones (add_isochrones('bt-settl'))
• The integrate_spectrum method is added to ReadModel for integrating the bolometric luminosity
• The param_inc and object_type parameters are added to the plot_posterior function
• Several enhancements for handling calibration spectra
• Some code maintenance and improvements in the documentation and tutorials