Added unit test for Props1SI function for pcrit input

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
R407F not in REFPROP

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed critical pressure for Methyl Stearate

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed EES wrapper to call correct functions in DLL

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