[Cython] Use scipy when necessary to support older Python versions
[Cython] Use scipy when necessary to support older Python versions

Fixes an incompatibility with Python 2.6 and 3.1. Scipy is not
required when using Python 2.7 or 3.2+.


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