Alias for the latest version of Emacs [1] for Mac.

This version of Emacs finally fixes the annoying $PATH problem that's
plagued Emacs on OS X for years, so we can launch Emacs from Finder or
`open -a` and not do any extra work.

  [1] https://github.com/railwaycat/emacs-mac-port
Add .zshenv for login shells