Turns out the volume bit was completely irrelevant.
First draft of IsothermalIsobaricStrirredReactor
Support dispatch to IsothermalIsobaric stirred reactor in base class
Oops, forgot to add enum
Distribute/install IsothermalIsobaricStirredReactor header
First pass at regression test for IsothermalIsobaricStirredReactor
Missing header

Arg, we need to include the header for all the reactors when dispatching
from the base class. Probably need to make a stirred_reactor.h that has
everything and just have the users use that. Not happy with that though.