Added assertions to check that some variables remain finite

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2281 02a645c2-efd0-11dd-984d-ab748d24aa7e
[Kinetics] Fixed a NaN result in falloff reaction rates

A NaN result could be caused by an underflow in the high-pressure rate
expression.

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2282 02a645c2-efd0-11dd-984d-ab748d24aa7e
[Matlab] Fixed integration failure in surfreactor example

git-svn-id: https://cantera.googlecode.com/svn/cantera/trunk@2283 02a645c2-efd0-11dd-984d-ab748d24aa7e