Add user-specified directories to the beginning of the search path
Add user-specified directories to the beginning of the search path

This way, users are able to override the defaults.

imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera