v1.12.21

-- Change installations based on Matlab runtime 2018b to 2017b. Homer3 exe based on 2018b doesn't work on Mac when clicking Edit Options button. Something got screwed up in the new matlab runtime.
-- Fix installation for Mac to be based on 2017b matlab runtime
-- Add installation files for deploying homer3 on windows and mac.
-- Add download/installation instructions to README.md