Messed up PATH setting 

This commit makes the instructions correctly add the new PATH to either .profile or .zprofile, for zsh and other shells. I got mixed up when writing the part about .zsh since I had to look into it while I was editing, and with the current instructions the line isn't added to .profile or added to .profile for zsh users that need it in .zprofile. I've reviewed the rest of the instructions and they should be good.