Working again for addTr

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added acetic acid from Piazza

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added more Helmholtz energy derivative tests

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Added PropsSI to MATLAB to close https://github.com/ibell/coolprop/issues/157

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Updated distro to include PropsSI function for MATLAB

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed bug with state class for py3 to close https://github.com/ibell/coolprop/issues/164

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Python 3.x compatibility changes

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
More py 3 compatibility changes

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
More py3 compatibility

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed infinite recursion causing stack overflow

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Almost done with third partial derivatives for associating fluids

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
Fixed citation to close https://github.com/ibell/coolprop/issues/165

Signed-off-by: Ian Bell <ian.h.bell@gmail.com>
More work on partials in AssociatingFluids.ipynb

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