a guide for setting up the toolchain on OSX

[weller]

This has been non-trivial so I wrote a guide. Hope this make someone's life easier.
http://www.pubpub.org/pub/esp32-osx-setup

[chrisfraser]

Great work weller. I went through this mission yesterday night and this would have helped a lot. Still trying to get both old and new SDKs to coexist nicely and work in eclipse. Will writeup a blog post once I am done.