Verify dependencies can be installed on MacOS via homebrew

[awillats]

Describe the solution you would like.
I like and use homebrew as my package manager on mac. It would be good to check everything can be installed via brew install xyz. I may be able to test this myself as I re-clone and setup development for ldsCtrlEst

Describe alternatives you have considered.
maybe we just stick to one package manager per broad OS category (linux, windows, mac/unix)

[awillats]

walking through the dependencies, i was able to get them all to install with homebrew:

brew install doxygen graphviz
brew install cmake pkg-config
brew install hdf5 armadillo openblas
brew install gcc 

gets the job done in a few lines (grouping packages loosely by function)

@mfbolus perhaps we add a "mac easy install" option which consists of a copy-to-clipboard codeblock with the brew instructions for all the packages?