Fixed the units for R134a conductivity critical term, and Nitrogen and CO2 as well (https://github.com/ibell/coolprop/issues/79)

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Merge branch 'master' of https://github.com/ibell/coolprop
Phase envelope closes properly!

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added HFC reducing parameters for HFC mixtures R404A, R410A, etc.

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
trying to validate the derivatives
Merge branch 'refs/heads/master' into derivToProps

Conflicts:
	CoolProp/gitrevision.h
Something is wrong with the second virial coefficient in the state class...