fix menu for the latest nw

Signed-off-by: Chris Granger <ibdknox@gmail.com>
fix the skins and themes to no longer use css variables as they've been removed in the latest versions of chromium. You can now use node-webkit 10+

Signed-off-by: Chris Granger <ibdknox@gmail.com>
Merge branch 'master' of github.com:Kodowa/Light-Table-Playground