Start implementing mixed precision to speed up computation
Clean up explicit casting for T_MIN and T_MAX
Clean up explicit casting for some physical constants
Clean up explicit casting for all other physical constants
Clean up explicit casting for mathematical constants
Reimplement B_Planck() to ensure that it works for single precision
Pull out the Gaunt factor from j_ff() for readability
Reimplement j_ff() to make it more robust
Reimplement j_synchr() to make it more robust
Group together big and small terms in j_synchr()
Place the length scale into j_ff() and j_synchr()
Add EPSILON to denominators in emissivities
Add EPSILON to denominators in fluid properties and radiative transfer
Rearrange and redefine macros in "src/gray.h" for easy merging
Merge branch 'harm' into develop

Conflicts:
	src/gray.h
Try using Taylor expansion to increase accuracy for small nu