Rename Tp to Ti for ion temperature
Implement the constant temperature plasma model
Rename Rw, Tw, and Ti_Te_w to Rf, Tf, and Ti_Te_f; f stands for funnel
Set Rf=0 or Tf=0 to skip the funnel
Decrease the default number of frequency bins, N_NU, to 5
Merge branch 'develop' into master
Fix bug: stop integrating a geodesic only if all frequencies are done
Increase the maximum allowed step size to speed up calculations
Place the image size parameter in Const so it is adjustable at runtime
Use lowercase t to indicate the temperatures are dimensionless
Skip the grid points that have unrealistic high temperature
Introduce a constant tgas_max to store the gas temperature threshold
Configure r_obs at runtime; output imgsz to "out.raw"
Merge branch 'develop' into master