Fix example of using --update option in README
Fix example of using --update option in README

Also use --requirements instead of --requirement
Don't use ./ for path in working directory

Milstein/nodeenv,jamesblunt/nodeenv,twmt/nodeenv,jamesblunt/nodeenv,jhermann/nodeenv,chriskuehl/nodeenv,asottile/nodeenv,simudream/nodeenv,asottile/nodeenv,chriskuehl/nodeenv,simudream/nodeenv,twmt/nodeenv,Milstein/nodeenv