TST: Add test for transition/cycle/operational flux relations

[nawtrey]

In T.L. Hill's book, "Free Energy Transduction and Biochemical Cycle Kinetics", he discusses simple relationships between transition fluxes, net cycle fluxes, and operational fluxes. Specifically, equations 3.3 and 3.4 show flux identities for a simple model. A test should be added that verifies these identities to further ensure consistency between various flux calculation types.

Test should be written to compare the output expressions, which can be compared with the normalization factor Sigma.

[nawtrey]

Additionally equations 3.5 and 3.6 show several relationships that should all hold if everything is internally consistent.

[nawtrey]

See the kda-examples PR #18 for example code comparing operational fluxes generated using both net cycle fluxes and net transition fluxes.

[nawtrey]

With GH-83 merged this is already more tractable, but I think we will wait until the net cycle fluxes are added (issue #57) to complete this.