Added documentation of reducing function derivatives

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Removed PHSU debug commands

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Tidied up speed test so that it will run

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added ECS parameters from Huber, IECR, 2003

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed ECS coefficients

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Updated T_reducing location for ECS

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