documentation and MathUnicode original files
http://tex.stackexchange.com/a/110043
also helpful
https://developer.apple.com/library/mac/technotes/tn2056/_index.html#//apple_ref/doc/uid/DTS10003085-CH1-SUBSECTION16
NB
- install under
/Library/Keyboard Layouts/to avoid disappearing layouts due to permission issues