Get Homebrew ruby on path?

[apjanke]

To get doc building working right on Mac under the Matlab Desktop GUI, we'll probably need to pull in Homebrew, because it's the Ruby that'll have bundler.

[apjanke]

This is tricky. The way to do this would be to check if bundler is installed and ruby is a new enough version, and if not, then search for a Homebrew installation and add that to $PATH with setenv(). But mucking around with the user's path or other environment variables automagically is a tricky thing that I'd rather not do.

Maybe we should just show users how to pull in Homebrew using their startup.m?

[apjanke]

I added a dev-kit/pull_in_homebrew_ruby.m that developers can call manually. I'm not comfortable calling it automatically yet.