Allow user-provided dependencies

[burgreen]

Thanks you for sharing this software!

Do any of your test cases replicate the P-V curve of a cardiac cycle?

I would suggest modifying your CMakeLists.txt to not require forced downloads of Eigen and the other 3 dependencies. If users have those packages already installed on their machines, let them supply the CMAKE_PREFIX_PATH and your CMakeLists.txt perform a find_package( xxx, REQUIRED) to locate the info.

[burgreen]

Found what I was seeking in your ClosedLoopHeartPulmonary class along with the paper reference!

[mrp089]

Thank you, @burgreen! It's a good idea to have a flag for user-provided dependencies.